PATCH: [perl #120723] Setting LC_NUMERIC breaks parsing of constants

PATCH: [perl #120723] Setting LC_NUMERIC breaks parsing of constants

This is the final patch for [perl #120723], and adds tests for it.

LC_NUMERIC Locale handling was broken for code during the compilation phase,
such as BEGIN {} blocks.  This is because, for some reason, perl.c set
LC_NUMERIC unconditionally back to the C locale right after locale
initialization.  I suspect that was to allow the core's parsing to not be
affected by locale.  However, earlier commits in this series have added code to
change/restore the locale during sections of the parsing where this might
matter, so this setting to the C locale is not needed.