Change MCDateTimeLocale to use StringRefs internally.

A number of the time/date routines have also been changed to deal in StringRefs. Additionally, g_english locale has been renamed to g_basic_locale in order to better reflect is usage and contents.
Fix an off-by-one error causing date parsing to fail

Number parsing would fail if it was the last item in the input string.
Fix a reference leak in MCD_convert_from_datetime
Merge branch 'refactor-syntax_unicode' into refactor-syntax_unicode_datetime
Fix to date/time handling for Unix systems

The Unix date/time routines were not fully updated previously.
Fix date/time formatting for Win32

Win32 date/time formatting code was not yet updated to use the StringRef date/time functions.
Merge branch 'refactor-syntax_unicode_datetime' into refactor-syntax_unicode_reviewed