swr/rast: WIP builder rewrite (2)

swr/rast: WIP builder rewrite (2)

Finish up the remaining explicit intrinsic uses. At this point all
explicit Intrinsic::getDeclaration() usage has been replaced with auto
generated macros generated with gen_llvm_ir_macros.py. Going forward,
make sure to only use the intrinsics here, adding new ones as needed.

Next step is to remove all references to x86 intrinsics to keep the
builder target-independent. Any x86 lowering will be handled by a
separate pass.

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