Fix constant propagation alg. in for statement like Mario suggestion.

Add note about How Constant Folding class is extended with a implementation constant propagation algorithm
by Mario de Sousa.

Add constant propagation algorithm for loop cycles.

Update symbol_c::first_file/last_file entries in list_c::add_element()

moved class to obtain datatype name (in char *) to get_datatype_info_c

merge

Fix comment about meet semilattice rules.

Complete fix initialize const_value.

Start to implement constant propagation algorithm.

Fix const_value field initialized.

Remove Ambiguous enumerate value in enum conversion functions.

Fix enum conversion function to string.

Fix struct generic_function_call_t initialize style.

Merge with Mario's changes.

Merge with Mario's repository.

Fix warning about call fprintf without format string.