swr/rast: FP consistency between POSH/RENDER pipes

swr/rast: FP consistency between POSH/RENDER pipes

- Ensure all threads have optimal floating-point control state
- Disable auto-generation of fused FP ops for VERTEX shader stage
- Disable "fast" FP ops for VERTEX shader stage

Reviewed-by: Bruce Cherniak <bruce.cherniak@intel.com>