On systems where both of the conditions

1. LD_LIBRARY_PATH does _not_ take precedence over DT_RPATH
  (e.g. Linux)
2. A previous libpython with the same major.minor is already installed
  (e.g. a previous version of this package)

hold, the built python will be linked with the installed libpython,
causing it to report an old teeny version in sys.version_info while
staging the install. Then "make package" fails with PLIST mismatches for
{,Pattern}Grammar.*.pickle.

pkgsrc knows which version we're building. Pass that down instead.

For platforms that weren't having this problem, no functional change
intended. For platforms that were, this simply restores "make package",
so no PKGREVISION bump.

(schmonz)