Update ancient glob/fnmatch implementations

Update ancient glob/fnmatch implementations

I looked again at trying to use the latest gnulib implemenentations
of GNU glob and fnmatch, and the effort required to extract them
from gnulib and make them portable to systems which don't support
configure is simply far too daunting for me.  However it's clear
that the previous implementations are growing too long on the tooth
to continue to be used without some maintenance, so perform some
upkeep on them.

- Remove support for pre-ANSI function definitions.
- Remove the obsolete "register" keyword.
- Assume standard ISO C90/C99 header file support.
- Assume standard ISO C "void" and "const" support.
- Avoid symbols prefixed with "__" as they're reserved.

* maintMakefile: Add a rule to verify lib has the latest content.
* src/dir.c: Use void* not __ptr_t which was removed.
* gl/lib/glob.c: See above.
* gl/lib/fnmatch.in.h: See above.
* gl/lib/glob.in.h: See above.
* gl/lib/fnmatch.c: See above.  Remove __strchrnul(): it is not
checked anywhere and is only used in one place anyway.