See #1328.

- amalgamate dlSym() and dlSymFound() into a single dlSymFind() backend
  with optional 'required' argument. This makes it possible to
  query and assign at once.

- replace (darwin) with (__APPLE__)
- replace (solarisGcc) with (__sun__ && __GNUC__)
- instead of 'darwin' -> '__APPLE'

- cease with passing a -D$(WM_ARCH) define since this adds no useful
  additional information and isn't used anywhere.

Reference
http://nadeausoftware.com/articles/2012/01/c_c_tip_how_use_compiler_predefined_macros_detect_operating_system

--

COMP: Extend size disambiguation on long (#1238)

- aids with portability and maintenance (#1238)

- silence clang warnings

- file-local static for saving the old action, which moves system
  dependencies out of the header files.

- set/reset of signals as file-local functions

STYLE: use csignal header instead of signal.h

- this improves overall consistency and is independent of higher level
  tagging as ASCII or BINARY for IFstream, OFstream etc.

- similar to the global '/' operator, but taking raw strings and not
  performing any stripping.

  Was previously a local function within POSIX.C, but it is useful enough
  to be in fileName itself.

- new regExpCxx wrapper for C++11 regex support with drop-in
  compatibility with existing code.

- regExpPosix (was regExp), for future phase out in favour of regExpCxx.

- The regExp header will continue to be used for defining an
  appropriate typedef corresponding to the preferred implementation.

- this information is more related to processor, not OS

- reduces some dictionary clutter and probably looks less confusing
  than having an ending that may not correspond to the current OS.

  Eg, "fvOptions" instead of "libfvOptions.so", "libfvOptions.dylib" ...

- convenience dlOpen method for multiple files

BUG: The ok_ flag was not being updated in the regExpCxx::set() method

- simplifies their use when reordering lists etc.
  (word, fileName, keyType, wordRe)

- "unfriend" IO operators for string types. They require no internal access

- add compile/uncompile methods to keyType for symmetry with wordRe

- when outputting keyType/wordRe, be more explicit about them using
  writeQuoted()

- more dictionary-like methods, enforce keyType::LITERAL for all
  lookups to avoid any spurious keyword matching.

- new readEntry, readIfPresent methods

- The get() method replaces the now deprecate lookup() method.

- Deprecate lookupOrFailsafe()
  Failsafe behaviour is now an optional parameter for lookupOrDefault,
  which makes it easier to tailor behaviour at runtime.

- output of the names is now always flatted without line-breaks.
  Thus,

     os << flatOutput(someEnumNames.names()) << nl;
     os << someEnumNames << nl;

  both generate the same output.

- Constructor now uses C-string (const char*) directly instead of
  Foam::word in its initializer_list.

- Remove special enum + initializer_list constructor form since
  it can create unbounded lookup indices.

- Removd old hasEnum, hasName forms that were provided during initial
  transition from NamedEnum.

- Added static_assert on Enum contents to restrict to enum or
  integral values.  Should not likely be using this class to enumerate
  other things since it internally uses an 'int' for its values.

  Changed volumeType accordingly to enumerate on its type (enum),
  not the class itself.

- with the 'cwd' optimization switch it is possible to select the
  preferred behaviour for the cwd() function.

  A value of 0 causes cwd() to return the physical directory,
  which is what getcwd() and `pwd -P` return.
  Until now, this was always the standard behaviour.

  With a value of 1, cwd() instead returns the logical directory,
  which what $PWD contains and `pwd -L` returns.
  If any of the sanity checks fail (eg, PWD points to something other
  than ".", etc), a warning is emitted and the physical cwd() is
  returned instead.

  Apart from the optical difference in the output, this additional
  control helps workaround file systems with whitespace or other
  characters in the directory that normally cause OpenFOAM to balk.
  Using a cleaner symlink elsewhere should skirt this issue.

  Eg,
      cd $HOME
      ln -s "/mounted volume/user/workdir"  workdir
      cd workdir
      # start working with OpenFOAM

- The problem is not 100% reproducible, but be somewhat conservative
  and now only close(stdin) for pure background (daemon-like) use of
  Foam::system(), where it can be useful.

  Using Foam::system() for launching background processes is currently
  only used for the doc browser.

- add additional control via a Foam::infoDetailLevel flag, which is
  supported by a 'DetailLevel' macro.  Eg,

      DetailLevel << "some information" << nl

- When infoDetailLevel is zero, the stdout for all Foam::system() calls
  are also redirected to stderr to prevent child output from
  appearing on the parent.

- close stdin before exec in system call.

- convenient way to temporarily suspend the SIGFPE handler.
  Eg,

      // Normal code with SIGFPE enabled ...
      sigFpe::set();

      {
          // Ignore SIGFPE in this scope ...
          sigFpe::ignore noFpeHandling;
          ...
      }

- make the purpose more explicit, and reduces some work for the
  compiler as well.

- was using st_atim instead of st_mtim for the nanoseconds

- value of followLink was being ignored (it was always being followed).

- controlled by the the 'printExecutionFormat' InfoSwitch in
  etc/controlDict

      // Style for "ExecutionTime = " output
      // - 0 = seconds (with trailing 's')
      // - 1 = day-hh:mm:ss

   ExecutionTime = 112135.2 s  ClockTime = 113017 s

   ExecutionTime = 1-07:08:55.20  ClockTime = 1-07:23:37

- Callable via the new Time::printExecutionTime() method,
  which also helps to reduce clutter in the applications.
  Eg,

     runTime.printExecutionTime(Info);

  vs

     Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"
         << "  ClockTime = " << runTime.elapsedClockTime() << " s"
         << nl << endl;

--

ENH: return elapsedClockTime() and clockTimeIncrement as double

- previously returned as time_t, which is less portable.

- generalize some of the library extensions (.so vs .dylib).
  Provide as wmake 'sysFunctions'

- added note about unsupported/incomplete system support

- centralize detection of ThirdParty packages into wmake/ subdirectory
  by providing a series of scripts in the spirit of GNU autoconfig.
  For example,

      have_boost, have_readline, have_scotch, ...

  Each of the `have_<package>` scripts will generally provide the
  following type of functions:

      have_<package>          # detection
      no_<package>            # reset
      echo_<package>          # echoing

  and the following type of variables:

      HAVE_<package>          # unset or 'true'
      <package>_ARCH_PATH     # root for <package>
      <package>_INC_DIR       # include directory for <package>
      <package>_LIB_DIR       # library directory for <package>

  This simplifies the calling scripts:

      if have_metis
      then
          wmake metisDecomp
      fi

  As well as reducing clutter in the corresponding Make/options:

      EXE_INC = \
          -I$(METIS_INC_DIR) \
          -I../decompositionMethods/lnInclude

      LIB_LIBS = \
          -L$(METIS_LIB_DIR) -lmetis

  Any additional modifications (platform-specific or for an external build
  system) can now be made centrally.

- a partial selection from https://github.com/mrklein/openfoam-os-x
  with adjustments. The primary purpose is to reduce header-level
  incompatibilities and to provide a common set of make rules to allow
  easier patching (or re-integration).

- this removes an OS-specific dependency (eg, drand48_r is not POSIX)
  and allows easier use of other random number generators.

  The Rand48 generator has identical behaviour and period as the
  lrand48() library routine, but holds its own seed and state
  (which makes it re-entrant) and can be combined with other
  random distributions.

  However, when using the modified form to obtain scalar values
  they will not be identical to what drand48() yields.

  This is because drand48() uses the raw 48-bit values to directly
  set the mantissa of an IEEE double where as the newer distribution
  normalizes based on the 32-bit value.

STYLE: simplify code in Random::shuffle and use Swap

- quick ignore of empty filenames.

- relocated some implementation details from POSIX.C to the
  fileStat class, where they make more sense.