[MachineOutliner] Inherit target features from parent function

If a function has target features, it may contain instructions that aren't
represented in the default set of instructions. If the outliner pulls out one
of these instructions, and the function doesn't have the right attributes
attached, we'll run into an LLVM error explaining that the target doesn't
support the necessary feature for the instruction.

This makes outlined functions inherit target features from their parents.

It also updates the machine-outliner.ll test to check that we're properly
inheriting target features.

llvm-svn: 345535