jpegenc: Add support for encoding from NV21 and NV12

https://bugzilla.gnome.org/show_bug.cgi?id=732870
qtdemux: fix language code parsing for 3-letter codes starting with 'a'

And handle special value for 'unspecified' explicitly.

https://developer.apple.com/library/mac/documentation/QuickTime/QTFF/QTFFChap4/qtff4.html
v4l2object: Remove is_active checks

These checks are no longer required with recent change to the bufferpool. This
should allow changing the configuartion, hence the way forward renegotiation
support.

https://bugzilla.gnome.org/show_bug.cgi?id=728268
v4l2: set debug messages according to device type and IO mode

https://bugzilla.gnome.org/show_bug.cgi?id=733616
v4l2sink: use directly 'obj' instead of 'v4l2sink->v4l2object'

https://bugzilla.gnome.org/show_bug.cgi?id=733616
v4l2object: query minimum required buffers for output

Some v4l2 devices could require a minimum buffers different from default
values. Rather than blindly propose a pool with min-buffers set to the
default value, it ask the device using control ioctl.

https://bugzilla.gnome.org/show_bug.cgi?id=733750
v4l2object: Don't share own pool if min exceed V4L2 capacity

If the minimum required buffer exceed V4L2 capacity, don't share down
pool. This allow support very high latency, like with x264enc default
encoding settings.

https://bugzilla.gnome.org/show_bug.cgi?id=732288
Revert "v4l2bufferpool: Workaround elements not requesting any buffers"

This was a tempory workaround, we should fix the encoders that do not
negotatiate the amount of buffers they need.

This reverts commit d03bcba3db15d06dbdea6b776a6f28ed2f03272a.
v4l2bufferpool: clear gcond
interleave: set output caps layout to interleaved

Set output caps layout independently from input caps layout which can
be either non-interleaved or interleaved.

https://bugzilla.gnome.org/show_bug.cgi?id=733866
ximagesrc: Add missing return value to Buffer dispose function

Depending ont he build, the method could return FALSE, hence never
free the buffers, or already TRUE and lead to a crash:

Fixes: https://bugzilla.gnome.org/show_bug.cgi?id=733695
ximagesrc: Fix warning about missing return value
Makefile: Add usage of build-checks step

Allows building checks without running them
rtph264pay: append profile-level-id to SDP

Append profile-level-id to SDP if available.

https://bugzilla.gnome.org/show_bug.cgi?id=733539
rtph264pay: unbreak au aligned byte-stream payloading
rtspsrc: Push the correct segment in TCP mode when seeking
Miscellaneous unref fixes (and possibly gst-indents *sigh*)