Log Message:
Update to 0.12.6:

Changes since 0.12.5:

- Fix some coverity issues.
- lazy-create XML namespaces so only used-ones are declared.

Bugs fixed in this release:
 - https://bugzilla.gnome.org/show_bug.cgi?id=705564
 - https://bugzilla.gnome.org/show_bug.cgi?id=730590
 - https://bugzilla.gnome.org/show_bug.cgi?id=730591
 - https://bugzilla.gnome.org/show_bug.cgi?id=731033

All contributors to this release:
 - Jens Georg <mail@jensge.org>