binary links in python26 portgroup

[Joshua Root]

I've added a new option "python.link_binaries" to the python26
portgroup, on by default, which in post-destroot will create
version-suffixed links in ${prefix}/bin/ to everything installed by the
port in ${python.prefix}/bin/.

I've adapted all py26-* ports that appeared to be affected by this
change, but if you maintain a port that uses the python26 group you may
wish to double check that it still does the right thing.

- Josh