Fix warnings when compiling matiec

Fix warning on nop statement at the end of function_block and program generated code

Adding double underscore in computed enumerated value to avoid conflict with other user defined identifiers

Add support for finding type of a constant enumerated value and managing conflict between same identifiers defined in different enumerated data types

Fix bug in declaring variable of enumerated type

Fix what I think is a bug (has not yet manifested itself).

Merging with Lauren't recent change.

Merging two previous commits.

Clean up some code.

Fix bug with array attribute in structure declaration

Add better comments, and change name of functions to clarify what they do.

Remove incorect debugging assertion.

Skip CONFIGURATION declarations in stage 3 for now, so semantic analysis does not stop when a configuration is encountered.

Fix bug when generating initial value for function return type when it is a complex type

Fix bug in debugging variable list compilation with structure and array disabling

Fix bug with TRUNC function and with type conversion functions called with constant as parameter