[Merge] [rt.cpan.org #88458] version XS routine revamp

This branch moves the version-specific XS and C functions in
universal.c and util.c into two new files, #included by the former.
This is to make it easier to keep core and CPAN in synch.  Up till
now, changes made to one had to be manually applied to the other
(except that was not actually happening all the time, so they got out
of synch).

A corresponding CPAN release has yet to be made.