/opt/local/bin/python2.5 as default MacPorts' "python" interpreter

[Guido Soranzio]

Currently there is no official "python" interpreter for MacPorts
(in the past there was a link to python2.3 even when python24
was installed, IIRC) but many Python programs (or their shebang lines)
expect a "python" command in the PATH, otherwise Leopard's python2.5
is picked from its symbolic link "/usr/bin/python" and they don't work
correctly.

This is the case, for example, of Sudoku and Chess in gnome-games.

I think that, similarly to the destroot phase of Tcl

(ln -s ${prefix}/bin/tclsh8.5 ${destroot}${prefix}/bin/tclsh)

an "/opt/local/bin/python" link should be created pointing to
the 2.5 version, as MacPorts' "default" Python version.