wined3d: Add a function to determine if a surface is the front or the backbuffer for a swapchain, and return the corresponding GLenum.

This implements a basic more, eg 'dir | more' or 'more file.c'
but it does not support the flags or keys which can control it.
Basically its not worth implementing those, as in some modes
we cannot read a single key, we have to wait for <enter> anyway.