regcomp.c: Silence compiler warning

This call to regclass_swash() is not using its return value, so don't
store it in a variable that is otherwise unused, which causes some
compilers to complain.
PATCH: [perl #119443] Blead won't compile on wince

This commit adds #if's to cause locale handling code to compile on
platforms that don't have full-featured locale handling.  The commits
mentioned in the ticket did not adequately cover these situations.