More preparation for 7.0 in versioning

More preparation for 7.0 in versioning

This modifies the macros introduced in
9b6e95106e18e4fd33678d0df9b2293fd4f8ab9c that allow one to determine how
the version of the perl currently being compiled compares to an
arbitrary one.  The modification is based on changes in the plan,
including renaming of variables.

This also introduces the use of '*' for the subversion (or micro as it
is now called) to make conversion from the soon-to-be deprecated
PERL_VERSION macro more rote, with less thinking involved.