r600g: initial support for geometry shaders on evergreen (v2)

r600g: initial support for geometry shaders on evergreen (v2)

This is Vadim's initial work with a few regression fixes squashed in.

v2: (airlied)
fix regression in glsl-max-varyings - need to use vs and ps_dirty
fix regression in shader exports from rebasing.
whitespace fixing.
v2.1: squash fix assert

Signed-off-by: Vadim Girlin <vadimgirlin@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>