svga: Allow DXPredCopyRegion for depth_and_stencil formats.
svga: Allow DXPredCopyRegion for depth_and_stencil formats.

DXPredCopyRegion supports copy between src and dst for depth_and_stencil
formats if src and dst have same formats.

tested ith piglit

v2: As per Brian's comment, allow DXPredCopyRegion for depth+stencil buffers
if the blit mask is PIPE_MASK_ZS.

Tested with piglit tests and added new piglit test
arb_framebuffer_object-depth-stencil-blit to test this particular testcase.

Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler