Add classes to print status of AST (use only for debugging!)

Remove all remaining NULL (undefined) datatypes from IL code.

Move is_datatype_valid/equal() to get_datatype_info_c

Fix bug related to support of SAFE datatypes.

Set datatype of il_intruction_c objects containing an ST operator.

Delete unused variables.

Use doubly linked connections for flow control graph (will be used later).

Remove deprecated search_expression_type_c

Deprecate use of search_expression_type_c (prepare for complete removal!).

Deprecate use of search_expression_type_c (prepare for complete removal!)

Deprecating use of search_expression_type_c, so it may later be deleted!

Merge

Add new get_datatype_info_c (preparing to remove search_expression_type_c)

Delete declaration of unused & undeclared functions.

Delete class elements that are not used (clean up code).

Add check whether external var matches to global var.

Also check FB passed as parameters in FB/Function calls (Thanks Andreas!)

Minor changes needed to build with pedantic flag.

Also check external/global variable consistency in configurations and FBs.

add method for printing class_name. USE ONLY FOR DEBUGING!

store POU reference to POU declaration instead of global var declarations.

Start declaration check class.

Start declaration check class.

Adjust coding style.