Fixing implementation of CU, CD, and CUD in standard library.

Deleting dead code.

Merging changes.

Added tracking of order by which tokens are processed by lexical analyser.
This helps in correctly formating error messages when constructs begin in one file, and end in another.

Adding tracking of filename in which token is located.

Reverted semantic error message so that Beremiz can parse them and that user can double-click on error message to open related POU and select the faulty line.

Fixing error message incorrectly changed in previous merge.

fixing C code generation of return_statement_c and exit_statement_c

merging the Edouard's version.

fixing exit_statement_c: produce 'break' instead of 'exit(0); (Thanks to Manuele)

Fixing code generation of standard conversion functions.

Re-generated std lib related code, with updated headers, updated all forgotten headers

Merged matiec library headers update from Mario to LGPL

Changing to LGPL for library functions.

Updating origin and license info of library fuctions.
Conclude missing counter FBs.

Leave standard function names hardcoded, as these are considered keywords even though
they may not be implemented in the library.