st/nine: Implement RESZ hack

st/nine: Implement RESZ hack

This D3D hack allows to resolve a multisampled
depth buffer into a single sampled one.

Note that the implementation is slightly incorrect.
When querying the content of D3DRS_POINTSIZE,
it should return the resz code if it has been set.
This behaviour will be implemented when state changes
will be reworked. For now the current behaviour is ok,
since apps use the D3DCREATE_PUREDEVICE flag when creating
the device, which means they won't read states and in exchange
get better performance.

Reviewed-by: Tiziano Bacocco <tizbac2@gmail.com>
Signed-off-by: Axel Davy <axel.davy@ens.fr>