[optimizing] Implement x86/x86_64 math intrinsics

Implement floor/ceil/round/RoundFloat on x86 and x86_64.
Implement RoundDouble on x86_64.

Add support for roundss and roundsd on both architectures.  Support them
in the disassembler as well.

Add the instruction set features for x86, as the 'round' instruction is
only supported if SSE4.1 is supported.

Fix the tests to handle the addition of passing the instruction set
features to x86 and x86_64.

Add assembler tests for roundsd and roundss to x86_64 assembler tests.

Change-Id: I9742d5930befb0bbc23f3d6c83ce0183ed9fe04f
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>