pkg_summary to include PKGBASENAME and PKGVERSION?

[matthew sporleder <msporleder%gmail.com@localhost>]

After a few threads about new pkgsrc tools have come out, it seems
that a common need is a way to define a package's name without a
version and that version string by itself.  It's pretty easy to derive
using PKGNAME, PKGPATH, FILE_NAME, whatever, but I think it's a
common-enough case that making the fields available by themselves is
worthwhile.

Matt