Tweak Mir2Lir::GenInstanceofCallingHelper for X86

Make this virtual, and split out the X86 logic.  Take advantage of SETcc
instruction for X86.

I don't think I can do much more due to need to preserve arguments for
the calls.

Change-Id: I10e3eaa61b61ceac384267e3078bb6f75c37cee4
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>
4 files changed