transform CASE into if()..else if().. -> fixes 2 bugs (1)case within case statements, and (2)repeated elements in case options

Initialise arrays to their correct default values - Fix bug introduced in commit 477393b00f95 (2014-11-16)

Fixed reset of current_varqualifier when generating global initializers, causin RETAIN and other option to be ORed and applied to all subsequent global variables.

Do fill/narrow datatype analysis algorithm for derived_datatype_identifier_c (fixes bug related to arrays of arrays that was generating incorrect C code).

Better identification of error location in some error messages.

Fix bug introduced in 2014/10/19, while adding support for REF() opertors -> datatype checking was not catching datatype inconsistency errors!

merge

Re-write and fix the logic of SFC action modifiers.

Correct the number given to actions in the #define's

Do not allow constant_propagation algorithm go into infinite loop when analysing code with circular references.

Do constant propagation of FBs instantiated in other FB or Programs, so that variable sized arrays can be declared in FBs too.

Do constant propagation of instantiated FBs, so that variable sized arrays can be declared in FBs too.

Let get_datatype_info_c handle variable sized arrays, even if constant folding is not yet done.

Correctly analyse external<->global var compatibility when using variable sized arrays (TODO: does not yet work for FBs!)

Add comment about bug that needs to be fixed later on.

Break constant_folding_c in two classes: constant_folding_c and constant_propagation_c