Don't test locales that are invalid for needed categories

Don't test locales that are invalid for needed categories

When looking for locales to test, skip ones which aren't defined in
every locale category we care about.  This was motivated by a Net BSD
machine which has a Pig Latin locale, but it is defined only for
LC_MESSAGES.

This necessitated adding parameters to pass the desired locale(s), and
renaming a test function to indicate the current category it is valid
for.