Stringify inline XML

Latest versions of mozjs (used by gnome-shell) drop support for E4X, so
using inline XML becomes a syntax error.

See-also: https://git.gnome.org/browse/gnome-shell/commit/?id=b908a3d70af279caad71a7ad87a301621b08271f
Merge pull request #149 from grawity/remove-e4x

Remove usage of inline XML