parser: Duplicate locale

The Release testing revealed that compiler might free temporary
std::locale instances sooner than we thought, exposing UaF.

On 64-bit arch, a reference takes 8 bytes, a std::locale copy takes 16
bytes. So duplicating a locale in each parser instance is not such a big
deal to risk an UaF.

Signed-off-by: Simon Rozman <simon@rozman.si>

include/stdex/parser.hpp

@@ -148,7 +148,7 @@ namespace stdex
 			interval<size_t> interval; ///< Test for interval
 
 		protected:
-			const std::locale& m_locale;
+			std::locale m_locale;
 		};
 
 		using parser = basic_parser<char>;