This uses a different shader than radeonsi, as we can't address non-256
aligned ssbos, which the radeonsi code does. This passes some extra
offsets into the shader.

It also contains a set of u64 instruction implementation that may
or may not be complete (at least the u64div is definitely not something
that works outside this use-case). If r600 grows 64-bit integers,
it will use the GLSL lowering for divmod.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>