nvc0: Handle ARB_conditional_render_inverted and enable it

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
llvmpipe/softpipe: enable ARB_conditional_render_inverted

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
docs: Update status of ARB_conditional_render_inverted

Done for: nvc0, softpipe and llvmpipe

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
nouveau: only enable the depth test if there actually is a depth buffer

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nouveau: only enable stencil func if the visual has stencil bits

The _Enabled property already has the relevant information.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>