Start using the called_fb_declaration annotation when generating C code from FB calls in ST.

Code cleanup: move datatype analysis to get_datatype_info_c

Fix bug-fix of previous commit.

Fix bug: allow use, as lvalues, structures/arrays inside FBs (e.g. fb1.struct1.r := 33.3).

Fix bug/issue #33 (correctly access struct/array variables declared inside a FB -> r:=FB1.FB2.struct1.array1[3] )

Add assertion suggested by Manuele.

merge

Use get_datatype_info_c::is_type_valid() to determine datatype validity
(some datatype bugs in source code were going unreported!)

Recursively check the datatype compatibility of values/expressions passed in function/FB invocations.

Change error message text so as to become more suitable to where they might occur in the source code.

Add code to check if an IN_OUT variable is being passed an IL list in formal IL FB/function invocations.

Generate correct error message when encountering IL lists embedded in IL formal invocations.

Fill in the 'datatype' anotation in the identifiers of symbolic variables.
(even though currently it is not being used).

Fix C code generation of FB invocation in IL.

Fix detection of datatype errors on IL conditional flow control operators (JMPC, RETC, ...)