This can't possibly do anything, since we fail texture creation for
WINED3DFMT_UNKNOWN. If texture creation with D3DFMT_UNKNOWN is actually
supposed to work, we should probably pick an appropriate format at creation,
instead of during CopyRects(). This code has existed in some form or another
since the initial version in commit 850a9429.
No tests, of course.

d3d10core: Add support for map_type flags D3D10_MAP_READ, D3D10_MAP_WRITE_NO_OVERWRITE and D3D10_MAP_DISCARD.