mesa: Add ARB_viewport_array plumbing
Define API connections to extension entry points added in previous
commits. Update entry points to use floating point arguments as
required by the extension.
Add get tokens for ARB_viewport_array state.
v2: Include review feedback.
v3 (idr): Fix 'make check'. Add missing Get infrastructure (some was
culled from other pathces).
Signed-off-by: Courtney Goeltzenleuchter <courtney@LunarG.com>
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>