eglglessink: eagl: fix eagl reuse by not releasing the context

It seems EAGL expects the application to simply ignore unused
EAGL contexts as the resources for it would be released when a new
context is set as the current one. Also move the egl extensions
querying to after a context is set to prevent crashes.

This makes the EAGL version of eglglessink reusable.
eglglessink: silence warnings building for RPI related to 'vcos_*'
eglglessink: fixes some warnings building on RPI
mpegvideoparse: fix caps extra unref

To call make_writable the element must own the caps ref, otherwise
it will unref someone else's ref
tsdemux: Fix caps string leak
mpegdemux: Don't build the MPEG TS descriptor parser

It conflicts with the one from the tsdemux plugin.
applemedia: remove the unneeded buffer's factory
applemedia: move VideoToolbox plugins to the public public

VideoToolbox is a public Framework in the 10.8 SDK. But we still
want to load its API dynamically to be able to build it
with and older SDK or with the iOS SDK, where it's still not public.
applemedia: fix planes offsets for the core video buffers
applemdia: replace private function with a public one

Replace the undocumented and private funtion
FigVideoFormatDescriptionCreateWithSampleDescriptionExtensionAtom
with a public equivalent
applemedia: fix vtdec for unsupported strides
applemedia:vtdec: add support for mpeg2 decoding
applemedia: use the best colorspace depending on the platform

Use the best colorspace on each platform to avoid colorspace
conversions between the decoder and the sink.
applemedia: use the recommended CoreFoundation Retain and Release
applemedia: fix duplicated symbols with applemedia
applemedia-nonpublic: fix symbols redefinition for objc files
videoparsers: fix duplicated symbols with libgstogg
rtpvp8: fix duplicated symbols with libvpx
h264parse: Update src pad caps when it was explicitly signaled

Fixes src pad caps aren't updated when converting from AVC to bytestream
and new caps had been received in the sink pad.

https://bugzilla.gnome.org/show_bug.cgi?id=698679
directdrawsink: respect PAR with coordinates