st/nine: Use bufs instead of Flags for Clear
st/nine: Use bufs instead of Flags for Clear

bufs doesn't contain depthstencil if
there is z buffer mismatch. This is the behaviour
we want.

Signed-off-by: Axel Davy <2b6ef604b998fb81662f85c329e4fc020eae8e5d@ens.fr>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler