- ITstream append() would previously have used the append from the
  underlying tokenList, which leaves the tokenIndex untouched and
  renders the freshly appended tokens effectively invisible if
  interspersed with primitiveEntry::read() that itself uses tokenIndex
  when building the list.

  The new append() method makes this hidden ITstream bi-directionality
  easier to manage. For efficiency, we only append lists
  (not individual tokens) and support a 'lazy' resizing that allows
  the final resizing to occur later when all tokens have been appended.

- The new ITstream seek() method provides a conveniently means to move
  to the end of the list or reposition to the middle.
  Using rewind() and using seek(0) are identical.

ENH: added OTstream to output directly to a list of tokens

---

BUG: List::newElem resized incorrectly

- had a simple doubling of the List size without checking that this
  would indeed be sufficient for the requested index.

  Bug was not triggered since primitiveEntry was the only class using
  this call, and it added the tokens sequentially.

- compacter messages in some cases

STYLE: simplify output handling of line numbers

- relax casting rules
  * down-cast of labelToken to boolToken
  * up-cast of wordToken to stringToken.
    Can use isStringType() test for word or string types

- simplify constructors, move construct etc.

- expose reset() method as public, which resets to UNDEFINED and
  clears allocated storage etc.

DEFEATURE: remove assign from word or string pointer.

- This was deprecated 2017-11 and now removed.
  For this type of content transfer, move assignment should be used
  instead of stealing pointers.

- creates a std::string with space-delimited tokens, which can be sent
  to another application or even re-parsed into tokens

- symmetric with writeRaw() etc for the output stream. These are
  methods that are not required by normal users, but which provide
  a finer granularity for reading.

- additional information about the current stream position when
  endList fails. This may help when tracing errors.

STYLE: change return type of beginRaw()/endRaw() to bool

- was of type Ostream& for output, but return value was unused.
  Having bool may be better for encapsulating logic

STYLE: remove unused Istream::readEndBegin() function

- a failed attempt to read a value (eg, word, label, scalar) from a
  stream now always provokes a FatalIOError.
  This helps avoid some difficult to trace input errors.

- simplify string output code

- for convenience and symmetry with OStringStream

STYLE: void return value for stream rewind() methods

- this makes it easier to design bidirectional streams

Avoids the clutter and maintenance effort associated with providing the
function signature string.

The new NotImplemented macro uses __PRETTY_FUNCTION__ for GNU compatible
compilers otherwise __func__ to provide the function name string.

This reverts commit c5bea524.

This reverts commit b18f6cc1.

- The lineNumber of token::undefinedToken was being changed instead of
  just the lineNumber of the return token.

- use List::first() and List::last() methods as well

- Istream and Ostream now retain backslashes when reading/writing strings.
  The previous implementation simply discarded them, except when used to
  escape a double-quote or a newline. It is now vitally important to retain
  them, eg for quoting regular expression meta-characters.

  The backslash continues to be used as an escape character for double-quote
  and newline, but otherwise get passed through "as-is" without any other
  special meaning (ie, they are *NOT* C-style strings). This helps avoid
  'backslash hell'!
  For example,
     string:   "match real dots \.+, question mark \? or any char .*"
     C-style:  "match real dots \\.+, question mark \\? or any char .*"

- combined subfiles in db/IOstreams, some had more copyright info than code
- OPstreamI.H contained only private methods, moved into OPstream.C

Are these really correct?
   IOstreams/Istream.H:#   include "HashTable.C"
   token/token.H:#define NoHashTableC