Extract version routines into two new files

Extract version routines into two new files

This is to make synchronisation between the CPAN distribution and the
perl core easier.

The files have different extensions to match what the CPAN distribu-
tion will have.  vutil.c is a separate compilation unit that the CPAN
dist already has.  vxs.inc will be included by vxs.xs (vxs.c is obvi-
ously alreday taken, being generated from vxs.xs).

In the perl core util.c includes vutil.c and universal.c
includes vxs.inc.