rtspsrc: set SSRC on caps if known
rtspsrc: srtp handling
rtspsrc: copy sticky events to ghostpad

When we expose internal pads as ghostpads, first copy the sticky events
so that we have the caps and segment etc.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=724712
rtspsrc: only expose streams on dataflow

Only probe on buffers, we don't want to expose the streams on events.
matroskamux: handle both sticky and non-sticky custom event
matroskademux: early sending pending codec-data for all streams

... at least before syncing across all streams might cause some gap
activity on any of those streams, notably sparse streams.

See also #712134
matroskademux: segment closing not needed in 1.x

... as sender should keep track of segment base accumulation.
Rather, it may have some adverse effects as a spurious segment event,
e.g. in collectpads.
pngdec: All frames are sync points
jpegdec: All frames are sync points
jpegpay: consider header len when calculating payload len

Fixed https://bugzilla.gnome.org/show_bug.cgi?id=726777
ximagesrc: Add ARGB/BGRA support
ximagesrc: only extrapolate alpha mask for 32-bit depth

Instead of passing bogus alpha mask values when there's no alpha.

https://bugzilla.gnome.org/show_bug.cgi?id=726833
v4l2: fix distcheck

Make sure ext/*.h are dist'ed
rtpmanager: copy sticky events when exposing pads in more places

https://bugzilla.gnome.org/show_bug.cgi?id=724712
v4l2: attempt to fix infinite (for small version of infinite) loop
v4l2src: Fix support for mpegts streams

It seems that GStreamer's mpegts elements (tsdemux, tsparse) require caps
`video/mpegts,systemstream=true`.  As far as I can see the significance
of systemstream is to indicate that this is a container format rather than
an elementary stream.  As this is the case (and I can't understand how it
could not be the case with mpegts) I add systemstream=true to v4l2src's
caps.

This allows v4l2src to be linked with tsdemux for playback from my
Hauppauge HD-PVR with the pipeline:

    v4l2src ! queue ! tsdemux ! video/x-h264 ! decodebin ! xvimagesink

In combination with the next commit this fixes using Hauppauge HD-PVR with
GStreamer 1.0+.
matroska-demux: add mapping for Opus audio codec

https://bugzilla.gnome.org/show_bug.cgi?id=727305
matroska-mux: add mapping for Opus audio

Might want to consider adding channels/rate
requirement to template caps, but requires
fixing up of encoder and parser first.
avidemux: Always set pixel-aspect-ratio on raw video streams

That field is mandatory in caps and if it is not present in the
AVI container, it means square pixels thus 1/1.
avidemux: Always set PTS=DTS on raw video streams