Fix more bugs in dsymtable_c (real semantics of std::multimap::lower_bound is not what was assumed!)

Fix counting bug in dsymbtable_c

Use duplicate symtable instead of symtable for enum constant value table (this will later allow us to detect semantic errors in IEC 61131-3 source code)

Move the enumerated_value_symtable to fill_candidate_datatypes_c, since it is only used there!

Make search_base_type_c a singleton!

Start datatype checking of variable declarations (for now, only seting symbol.datatype of enumerations)

Do datatype checking of enum values defined inside anonymous enumeration types (i.e. enum types defined inside a VAR ... END_VAR daclaration).

Added support for testing BCD value validity in BCD_TO_UINT function

Fixed bug in DATE_AND_TIME_TO_TIME_OF_DAY and DATE_AND_TIME_TO_DATE when date and time is before 1970-01-01-00:00:00

Fix warning message when declaring global variables in configuration

Removed unused variable

Replacing libc time functions for date <-> timespec translation by platform and localtime independant implementation

Removed files generedted by autoconf, should not be in repo

Fixed timegm usage incompatible with mingw, reverted to mktime in case mingw is detected

Fix in accessor undefined init methods for function block global instances

Fix undefined function toupper in iec_std_lib

Adding support for declaring function block instances as global and external variables

Fix DATE conversions standard functions

Fix definition of BCD to ANY_UINT and ANY_UINT to BCD conversion standard functions

Fix indentation in SFC SL qualifier code generated

Fix indentation and unused variable warning in SFC generated code

Fix pragma with double bracket token stripping

Fix some warning about loss of precision data in iec_std_lib.h file.

Fix typo.