This is useful when implementing custom retransmission mechanism like
RIST to prevent RTCP from being produces for the retransmitted SSRC.
This would also be used in general for various purpose when customizing
an RTP base pipeline.

If it goes over 2^15 packets, it will think it has rolled over
and start dropping all packets. So make sure the seqnum distance is not too big.

But let's not limit it to a number that is too small to avoid emptying it
needlessly if there is a spurious huge sequence number, let's allow at
least 10k packets in any case.

Recent changes in ccextractor were attaching timecode meta to the closed
caption track. We shouldn't write timecode information for the closed
caption trak.

The deprecated debug visualizer was removed.

error: this decimal constant is unsigned only in ISO C90 [-Werror]

It is possible that PulseAudio adds formats that are not yet supported
in pulsesink, and in those cases, we want to gracefully skip them rather
than cause an assert on a NULL caps.

Reapply 3d708a5b in the correct place
after the iOS additions.

And let it the oportunity to get its other pad linked

Example:

```
$ gst-launch-1.0 uridecodebin uri=file:///home/thiblahute/gst-validate.save/gst-integration-testsuites/testsuites/../medias/defaults/flv/819290236.flv caps=audio/x-raw expose-all-streams=FALSE ! fakesink
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
ERROR: from element /GstPipeline:pipeline0/GstURIDecodeBin:uridecodebin0/GstDecodeBin:decodebin0/GstFlvDemux:flvdemux0: Internal data stream error.
Additional debug info:
../subprojects/gst-plugins-good/gst/flv/gstflvdemux.c(2760): gst_flv_demux_loop (): /GstPipeline:pipeline0/GstURIDecodeBin:uridecodebin0/GstDecodeBin:decodebin0/GstFlvDemux:flvdemux0:
streaming stopped, reason not-linked (-1)
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...
```

Modify the caps string to allow width and height greater than 4096.
There is no need to restrict it since the matroska format allows the
width and height values to be up to eight bytes long, and this also
applies to the webm subset of the format.

Fixes gstreamer/gst-plugins-good#550

Tested with cross-ios-arm64 and cross-ios-x86, since those two are the
only archs shipped with the official Qt binaries.

This was originally added for fixing conflicting definitions between
Android and Qt, but times have changed and now this breaks the build
on iOS:

 [...]/OpenGLES.framework/Headers/ES3/gl.h:1006:48: error: unknown type name 'gst_qt_GLsync'
 GL_API void           GL_APIENTRY glGetSynciv (GLsync sync, GLenum pname, GLsizei bufSize, GLsizei* length, GLint* values)   OPENGLES_DEPRECATED(ios(7.0, 12.0), tvos(9.0, 12.0));
                                               ^
 ../ext/qt/gstqtgl.h:49:16: note: expanded from macro 'GLsync'
 #define GLsync gst_qt_GLsync
                ^
 6 errors generated.

Instead, we simply avoid defining GLsync ourselves if we're using Qt.

When multiple nals are aggrgated, the marker bit should be associated only
with the last NAL of the packet. Otherwise we may break rendering in with
AU alignment.

Only forward the marker for the last NAL of the STAP-A. Otherwise each NAL
endup being assumed to be a full frame which may break rendering.

Fixes 557

We are missing a sample to test this, but a fix has been made, so add a
todo.

Related to #557

This is especially never available on iOS.

Allow fallback to orc subproject if any.
Additionally 'dependencies' keyword is removed from find_library,
because it's invalid keyword for find_library.

It makes no sense for a decoder to output a BYTES segment, and
many elements one would plug downstream of a video decoder assume
the segments they receive are in TIME format, for example this fixes:

gst-validate-1.0 filesrc location=opacity01.svg ! gdkpixbufdec ! \
videobalance ! videoconvert ! fakesink

In that case, videobalance was emitting an assertion when trying to
call gst_object_sync_values()

Tested with Cerbero.

Needs gnustl for C++ STL support, which is the GNU STL on Android API
19 and older, and is a wrapper for the llvm-libc++ STL on newer APIs.

QtGui C++ templates use GL functions, so GLESv2 is needed at link time

regardless of whether they're positioned, since positioning
with a 1 channel stream doesn't change anything.

The Qt Android integration is now signalled with HAVE_QT_ANDROID

See: gstreamer/gst-plugins-good!86

There was a mismatch between the .pc files generated by
autotools and by meson that would lead to meson not detecting
that opengl api is available even though it is, if -base was
built with autotools. The mismatch has now been rectified in
-base, so we need to update for that.

This is mostly for consistency, this problem didn't seem
to affect anything in -good.

See gstreamer/gst-plugins-bad#871

Fixes FIXME.

And rename x11 option to ximagesrc.

Fixes #553

The android code path is slightly different than the EGLFS one,
so I added previously a HAVE_QT_ANDROID define for use with qmake.
Here I also add it in meson, although I expect nobody will ever use
meson to build this, as it's complicated.