Make it possible to have all libgstvaapi backends (libs) access to a
common GstVaapiMiniObject API and implementation. This is a minor step
towards full exposure when needed, but restrict it to libgstvaapi at
this time.
Make sure that libgstvaapi private headers remain internally used to
build libgstvaapi libraries only. All header dependencies were reviewed
and checks for IN_LIBGSTVAAPI definition were added accordingly.
Also rename GST_VAAPI_CORE definition to IN_LIBGSTVAAPI_CORE to keep
consistency.
Drop support for user-defined data since this capability was not used
so far and GstVaapiMiniObject represents the smallest reference counted
object type. Add missing GST_VAAPI_MINI_OBJECT_CLASS() helper macro.
Besides, since GstVaapiMiniObject is a libgstvaapi internal object, it
is also possible to further simplify the layout of the object. i.e. merge
GstVaapiMiniObjectBase into GstVaapiMiniObject.
Introduce a new reference counted object that is very lightweight and
also provides flags and user-data functionalities. Initialization and
finalization times are reduced by up to a factor 5x vs GstMiniObject
from GStreamer 0.10 stack.
This is a libgstvaapi internal object.
