tmp: Improved reference count checks to provide better error diagnostics

in case of tmp misuse.

Simplified tmp reuse pattern in field algebra to use tmp copy and
assignment rather than the complex delayed call to 'ptr()'.

Removed support for unused non-const 'REF' storage of non-tmp objects due to C++
limitation in constructor overloading: if both tmp(T&) and tmp(const T&)
constructors are provided resolution is ambiguous.

The turbulence libraries have been upgraded and '-DCONST_TMP' option
specified in the 'options' file to switch to the new 'tmp' behavior.