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
v4l2: Fix support for caps without width, height, framerate or format

For format like mpegts, width and height is rarely in the negotiated caps. This
patch fixes failure when setting format, and prevent introducing width, height,
framerate and format to the caps when fixating.

https://bugzilla.gnome.org/show_bug.cgi?id=725860
jitterbuffer: demote warning to debug

For TCP, it is normal that we don't have timestamps so don't WARN on
it.
rtspsrc: cleanup stream_free function

There is no reason to NULL all fields, we will free the stream anyway.
rtspsrc: free the srtpdec element
rtspsrc: create and send the RTCP encryption key

Create and make a key for encrypting the RTCP packets back to the server
and wrap this in a MIKEY message that we send as a header in the SETUP
request.
rtspsrc: don't put spaces in keymgmt header
rtspsrc: make random number for the CSB

As recommended in the RFC
rtspsrc: send sender SSRC in the MIKEY message

Allocate a new SSRC for our RTCP messages back to the server and set
this in the MIKEY message.
rtspsrc: update for new MIKEY API