This CL introduces the X86Inst templates. The previous implementation relied on template specialization which did not played nice with the new design. This required a lot of other boilerplate code (i.e., tons of new named constructors, one for each X86Inst.)

This CL also moves X8632 code out of the X86Base{Impl}?.h files so that they are **almost** target agnostic. As we move to adding other X86 targets more methods will be moved to the target-specific trait class (e.g., call/ret/argument lowering.)

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4077
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/1216933015.