libgstreamer currently exports some debug category
symbols GST_CAT_*, but those are not declared in any
public headers.
Some plugins and libgstvideo just use GST_DEBUG_CATEGORY_EXTERN()
to declare and use those, but that's just not right at
all, and it won't work on Windows with MSVC. Instead look
up the categories via the API.
Make a new refcounted xvcontext object that handles the X connection.
Use the xvcontext to allocate images and windows. Move some code
around so that all X calls are made from the xvcontext object.
Make a GstXvImageAllocator object that allocates images from the xvcontext. We
can implement a copy function now for these memory objects now.
Make the bufferpool use the xvimageallocator object for its images.
Improve bufferpool handling in ximagesink.
Implement bufferpool handling on xvimagesink.
Based on patches from benjamin gaignard <benjamin.gaignard@linaro.org>
