cvs: Rebuild without gnuregex library

cvs: Rebuild without gnuregex library

CVS is the last software that uses the libgnuregex.  In fact, it only
used one of its headers, and it wasn't necessary.  This commit clears the
way for libgnuregex to be removed from base by restoring the use of the
provided regex source files.

Review showed:
* config.h.proto file was out of date
* alloca.h allowed macro redefinition
* prepend_args.* files weren't used
* doc files were generating warnings, maybe due to new texinfo upgrade
* MD library linking unnecessary
* other minor issues