Use glib >= 2.32 semantics for GMutex and GRecMutex wrt. initialization
and termination. Basically, the new mutex objects can be used as static
mutex objects from the deprecated APIs, e.g. GStaticMutex and GStaticRecMutex.
Move display types from gstvaapipluginutil.* to gstvaapidisplay.* so that
we could simplify characterization of a GstVaapiDisplay. Also rename "auto"
type to "any", and add a "display-type" attribute.