winemac: Defer attaching OpenGL context to a view which is zero-sized or outside its window's bounds.

That fails with the dread "invalid drawable" message.

It has a non-object pointer from the caller, so it can't allow the caller
to continue until it's finished with it.  Also, it discards events from the
event queue and we don't want the caller to process them first.

Fixes brokenness introduced by 784a9139.

This has only ever worked for render targets, and only through the
glDrawPixels codepath, which was removed long ago.

wined3d: Get rid of the redundant texture_name and texture_name_srgb fields in struct wined3d_surface.