Log Message:
If GNU_PROGRAM_PREFIX is not "g" or not set, then still install
with "g" prefix.  Allow this to be optionally forced by defining
GTAR_PROGRAM_PREFIX.  If GTAR_PROGRAM_PREFIX is set to nothing,
then conflict with pax, because both install a "tar".

So now the default is to install as "gtar" even if GNU_PROGRAM_PREFIX
is set to "".

Bump package revision for this.

This is for part of my PR #22693.