Add unit tests for specific instruction patterns that the x86

assembly inspection class is designed to detect.  This is only about
half of the instructions that it needs to recognize - I'll complete
this in a separate checkin.

The larger full-function style test cases I'd checked in previously
covered nearly all of these already, but I wanted simpler test cases
too, so if they fail in the future, it will be easier to spot the
issue.

llvm-svn: 283010