GDBus: ignore qualified XML tags and attributes

Ignore qualified (in the XML namespace sense) tags and attributes when
parsing D-Bus introspection XML.

This will allow people to add custom tags and attributes to their D-Bus
interfaces without tripping up GDBus.

https://bugzilla.gnome.org/show_bug.cgi?id=665634
glib-compile-schemas: ignore qualified tags/attrs

Ignore qualified (in the XML namespace sense) tags and attributes when
compiling GSettings schemas.

This will allow people to add custom tags and attributes to their schemas
without tripping up the compiler.

https://bugzilla.gnome.org/show_bug.cgi?id=635641