Call the default event handler for unknown events.

Move the code to find the tags and to typefind the data into a separate
function. Call this function from the loop function.

Start a task to perform the pulling and typefind of the tags.

We don't want to blindly forward all queries.

They're now {audio,video}/x-raw, not {audio,video}/x-raw-*

https://bugzilla.gnome.org/show_bug.cgi?id=668682

They're now video/x-raw, not video/x-raw-* anymore.

https://bugzilla.gnome.org/show_bug.cgi?id=668682

https://bugzilla.gnome.org/show_bug.cgi?id=668682

We can't use G_DEFINE_*TYPE here because we need the klass in the _init
method to get to the padtemplates. Fixes 'GstTagDemux subclass GstTagDemux
did not set up a {sink,src} pad template' warnings.

videoconvert does not work with GRAY formats yet so don't try to run the unit
test with it.

Conflicts:
	ext/vorbis/gstvorbisparse.c
	gst-libs/gst/video/video.c
	gst/videoscale/gstvideoscale.c
	sys/v4l/gstv4lxoverlay.c
	sys/v4l/v4l_calls.c
	sys/v4l/v4lsrc_calls.c
	tests/check/libs/video.c

Only return LIKELY probability if we've seen an SPS, PPS and an
IDR slice nal, i.e. try harder to avoid false positives such
as with certain VC-1 files.

https://bugzilla.gnome.org/show_bug.cgi?id=668565

Fix merge error from commit fb6d0905