add gobject-introspection

needed for newer rygel builds
from https://github.com/aandyl/openwrt-packages

gobject introspection is used by the host builds of gssdp and gupnp* to
generate Vala API definitions (.vapi)

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>
rygel: add patch for vapidir

taken from
https://github.com/aandyl/openwrt-packages/
http://patchwork.openwrt.org/patch/3178/

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>