swift234

Consistently set target, CPU, and subtarget options in AOT and JIT mode.

Factor out the code that sets up llvm::TargetOptions and SubtargetFeatures via Clang, and reuse it in immediate mode to properly set up the ExecutionEngine to be consistent with the environment we emitted code for. This makes it so that we can use code that lowers to, for instance, SSE3 intrinsics, in particular stuff like GLKit code imported from Clang.

Swift SVN r23646