wined3d: Only invalidate STATE_INDEXBUFFER for the current context in buffer_create_buffer_object().

wined3d: Rewrite surface_modify_location() on top of surface_validate_location() and surface_invalidate_location().

Otherwise invoking winegcc on any platform where our first guess at
the link options fails results in a lot of confusing error messages.

This stops the tested gcc command from issuing a warning on Solaris.

It's not worth printing a FIXME for every VARTYPE we don't happen to
list in the switch statement.