Modify locale code to defend against possibility that it was compiled

Modify locale code to defend against possibility that it was compiled
with an -fsigned-char/-funsigned-char setting opposite to that of libc,
thus breaking the convention that 'undefined' values returned by
localeconv() are represented by CHAR_MAX.  It is sheer stupidity that
gcc even has such a switch --- it's just as bad as the structure-packing
control switches offered by the more brain-dead PC compilers --- and
as for the behavior of Linux distribution vendors who set RPM_OPT_FLAGS
differently from the way they built libc, well, words fail me...