Javascript metamodule

This adds a new modules file with a target meta-gtk-osx-javascript
which builds GJS and its dependencies (mozjs17, nspr).

This target exists in modulesets-stable (GJS 1.38.1) and modulesets
(gnome-3-10 branch), but not yet in modulesets-unstable; I haven't
gotten mozjs24 to build yet. In both cases, mozjs17 and nspr are built
from tarballs.
js24 and Javascript for modulesets-unstable

Master-branch GJS requires js24 instead of js17. This adds js24 to
all three modulesets (since it builds from a tarball anyway) and also
adds a meta-gtk-osx-javascript target for modulesets-unstable, since
we can now build GJS from master.
Merge pull request #24 from ptomato/javascript-metamodule

Javascript metamodule
Webkit libstc++ for clang.
Update Python version to 2.7.6., use https.
Add boehm-gc (garbage collection) for guile2.

Mind, guile2 still won't build, but that's another issue.
Fix libffi autogen template to something that works.
Fix up Glade so that it builds.

Unfortunately this loses the Mac menu customization.
Update doap to reflect correct bug tracker.
Fix wrong tarball directory and name for gnome-icon-extras.

Thanks to Jesse van den Kieboom for noticing.
Update readline to 6.3, which actually builds correctly on 10.9
Add patch to fix building Guile 2.0 for i386 with Xcode 5.1 and later.
Update Python to 2.7.8; earlier versions don't build with Xcode 6.