Fix handling of IL parenthesized expressions in generate_c_il_c

Fix processing of TIME literals (submited by Andreas)

Fix flow control analysis of IL simple instructions (i.e. IL instructions inside parenthises!)

Comment out invalid assertion.

Code cleanup: get the datatype of each entity off symbol->datatype (set in stage3 datatype checking), instead of determining it again in stage4. (NOTE: handling of IL parenthesized expressions is not working! Will be fixed later.)

Major code cleanup: IL code generation now uses symbol.datatype (filled in during stage3 data type checking) instead of determining the symbol's datatype by itself.

Do not repeat narrow algorithm for ST code, and better comments.

New visitor classes missing from previous commit.

Remove line printing debug info.

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).