We now only delete the node contents in these functions.

Not only is it not related to property set storages, it's also not the root
of the tree that's used to search for elements.

wgl: Make sure we set a valid value for GLX_DRAWABLE_TYPE. Right now we default to 0 which is illegal.

wgl: None of the WGL_render_texture attribute values makes sense for GLX_X_RENDERABLE, so get rid of it.

Found by Valgrind.

Found by Valgrind.