UTF8ization of PlibC

Originally from http://sourceforge.net/tracker/index.php?func=detail&aid=3465706&group_id=137319&atid=738312
Some fixes were added
Add generated files
Don't use -no-undefined during configure as gcc don't like it
Re-arrange configure.in + add new define for MinGW
Regenerate files
Define error values only if not defined and shift error numbers so they not interfere with system errno.h
Detect more MinGW-w64 declarations and exclude symbols
Add -DUSE_IPV6 to include IPV6 parts during lib build
Fix various warnings
Fix libintl usage
Fix more potential bugs
Use correct variable type.
struct _stat and stat are different depending on defines.
MinGW-w64 have functions _stat, stat, _wstat and wstat, but MinGW32 have no wstat.
Make PlibC really compatible with Win64
Properly use x64 mode in string.c
Add some IPv6 compatibility
Fix missing and mistyped functions in public header
Replace very weak pseudo random generation with MS function
Remove unused typedef
Add lib identification to header
This will allow to check lib capabilities as compile-time.
Remove variables defined in system headers