Fix bug introduced when adding support for relaxed datatype model: change derived_datatype_identifier_c to identifier_c when used as an identifier

Add a pre-parsing phase to stage1_2 (allows source code that references POUs and datatypes before they are declared)

Comment out unused and buggy code.

Update the comments in source code.

Fix bug introduced when adding support for relaxed datatype model. Code cleanup.

Fix main state machine in flex (states were being pushed without being poped from the stack)

merge

Make the relaxed datatype model a runtime option (off by default)

Add support for relaxed datatype model for array datatypes.

fix bug introduced a few commits ago: do not print the first char ('%') of a direct_variable_c (e.g. skip % in %IW4.2)

fix code generation when dereferencing pointers (ref_to) to arrays (ref_to_array^[5])

Fix bug: set the scope annotation in deref_operators used inside structs

Editing of error message to make it more clear.

Filling of symbol->scope annotation moved from narrow to fill_candidate_datatypes_c (became possible because narrowing of struct, array and symbolic variables is now done directly in fill_candidate_datatypes_c)

fill_candidate_datatypes_c now uses search_varinstance_decl_c instead of search_varfb_instance_type_c (moving towards deprecation of search_varfb_instance_type_c)

Do the full fill_candidate/narrow_datatype algorithm for all fields of a structured variable in the fill_candidate_datatypes_c
Allows us to remove temporary code from the search_varfb_decl_c

Fix bug with multple dereferencing (bool_var := bool_ptr_ptr^^;)

Fix bug: Add support for de-referencing pointers to struct (struct_ptr^.elem1) when used inside FB.
Note that multiple de-referencing of structs (struct_ptr_ptr^^.elem) is not supported inside FB code (this would need BIG changes to the compiler!)

Fix bug: add support for dereferencing of REF_TO to REF_TO xxx (e.g.: bool_var := ref_to_ref_to_bool^^;)

Turn support of derefencing operator '^' an option (default is not supported).

Add support for de-referencing of REF_TO datatypes (Note: dereferencing of arrays and structs not yet supported!)

Add support for REF_TO inside arrays and structs (a non-standard feature!)

Code cleanup: with the introduction of anotation_map[], generate_c_vardecl_c can now derive directly from generate_c_base_c

Fix typos in comments

Add comments, and make get_datatype_id_str_c equivalent to get_datatype_id_c

Fix calling of functions whose parameters are of an implicitly declared datatype (currently only makes sense for REF_TO datatypes, but may make sense to other datatypes too if the datatype model is changed in the future).

fix indentations.

in lvalue, add check for REF() fucntion invocation, and the NULL literal