Fix formts for various GST_DEBUG et al. invocations. More precisely,
make size_t arguments use the %zu format specifier accordingly; force
XID formats to be a 32-bit unsigned integer; and fix the format used
for gst_vaapi_create_surface_with_format() error cases since we have
been using strings nowadays.
Make sure to create the GLX context once the window object has completed
its creation. Since gl_resize() relies on the newly created window size,
then we cannot simply overload the GstVaapiWindowClass::create() hook.
So, we just call into gst_vaapi_window_glx_ensure_context() once the
window object is created in the gst_vaapi_window_glx_new*() functions.
Drop obsolete GST_VAAPI_IS_xxx() helper macros since we are no longer
deriving from GObject and so those were only checking for whether the
argument was NULL or not. This is now irrelevant, and even confusing
to some extent, because we no longer have type checking.
Note: this incurs more type checking (review) but the libgstvaapi is
rather small, so this is manageable.
