Support CMOV for x86 Select

If possible, generate CMOV to implement HSelect.  Tricky cases are a
long or FP condition (no single CC generated), FP inputs (no FP CMOV)
and when the condition is a boolean or not emitted at the use site.
In these cases, keep using the existing HSelect code.

Change-Id: I4ff1e152b8ef126fbbabeb3316e9e2b6a6b74aeb
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>