perl5.000 patch.0e: fix various non-broken things in the x2p/ directory

perl5.000 patch.0e: fix various non-broken things in the x2p/ directory

This patch fixes various non-broken things in the x2p/ directory.
Mostly, I've supplied function prototypes to satisfy particularly
picky compilers.

I've also updated Makefile.SH to know that the byacc-generated a2p.c
is now included with the distribution so that we no longer need to go
looking for yacc/bison/byacc and deal with various library issues or
command line options to support those various compiler compilers.

I've included a2p.c generated by byacc-1.9.  Larry, feel free to
use your own from byacc-1.8 instead.