d3d12: Support packed scalars in ubos and fix additional binding-slot-0 issues
This merge is dependent on !144 (merged).
With this change we are down to 16 failing Piglit uniform 'glsl' tests out of 598 and fixes a bunch of crashing tests. There remain 16 failing test cases but no crashes. Not yet clear if the failing tests are directly related to ubo's.
Edited by Bill Kristiansen