codecparser: h264: Use proper bit_reader api while parsing buffering_period SEI

https://bugzilla.gnome.org/show_bug.cgi?id=734970
tsdemux: remove pads when resetting the element

Otherwise the pads will be there if it is restarted and the stream
can be a completely different one.

https://bugzilla.gnome.org/show_bug.cgi?id=734394
glimagesink: unref the window on navigation event

plugs a memory leak
glvideomixer: get the attribute from the correct shader
glvideomixer: don't clobber unnecessary GstVideoInfo fields

otherwise we might clobber other important fields such as the frame rate.
glvideomixer: avoid gl resource race condition between different thread

https://bugzilla.gnome.org/show_bug.cgi?id=734830
glmixer: unref the GstGLUpload in the pad if freed while running

Dynamic pipelines that get and release the sink pads will finalize
the pad without going through gst_gl_mixer_stop() which is where the
upload object is usually freed.  Don't leak objects in such case.
gl: don't take an extra ref on the display on set_context

gst_context_get_gl_display() returns a ref.  Don't take another in
gst_object_replace().
dashdemux: push language code tag

Language code tag is retrieved from the AdaptationSet language
property.

https://bugzilla.gnome.org/show_bug.cgi?id=732237
dashdemux: read language from ContentComponent node as a fallback

If the language is not specified in the AdaptationSet, use the ContentComponent
node to get it. We only get it if there is only a single ContentComponent as
it doesn't seem clear on what to do if there are multiple entries

https://bugzilla.gnome.org/show_bug.cgi?id=732237
dashdemux: unref pad reference when removing internal source in error

Avoids leaking the pad in error situations
gl: add prototypes for KHR_debug/ARB_debug_output
glcontext: implement the debug callback

For both GL_KHR_debug and ARB_debug_output.  This allows us to
receive errors and other hints from the GL instead of querying after
every GL operation.
gl: add prototype definition for KHR_debug
gl: check null before unref GstGLDisplay
glshader: expose opengl handle in getter

https://bugzilla.gnome.org/show_bug.cgi?id=734482
glimagesink: expose context

* expose context in draw / reshape callbacks
* add context property

https://bugzilla.gnome.org/show_bug.cgi?id=734482
examples: fix gtk+ 3.14 deprecation error

https://developer.gnome.org/gtk3/3.13/GtkWidget.html#gtk-widget-set-double-buffered

https://bugzilla.gnome.org/show_bug.cgi?id=734482
gstopengl: add introspection support

https://bugzilla.gnome.org/show_bug.cgi?id=734482
dashdemux: fix abort in error code path with newer glib

Don't forget to unlock mpd client again when erroring out.
Fixes abort when g_mutex_clear() is called on a locked mutex.