New python2 patch (fix mistake in 91da3a80)

This should have been added as part of 91da3a80.
Single-line pkgdesc
Switch to Git version; release 20131015-1

As it turns out, using the "released" JHBuild sources is not supported;
they're not kept up-to-date. JHBuild is intended to be built from Git.
Whoops.

Also, build GNOME 3.12 instead of 3.10.