Change enum names for new locale function parameters

Change enum names for new locale function parameters

Earlier in the 5.27 series, I introduced Perl_langinfo which calls
the system nl_langinfo() on platforms that have it, and emulates it
otherwise.  For each enum parameter 'foo', I made an equivalent
parameter PERL_foo.  I did this so that no conflicts would arise if
any 'foo' were negative.  This is less than ideal to have to rename the
parameters.

In looking further, I realized that perl has always excluded the
possibility of negative values for 'foo', so my precaution is
unnecessary.  And before this new code is released is the time to fix up
the interface.