Replace old bitfield test.
Replace old bitfield test.

 - Change hardcoded assembly instructions to a use of 'opt' (still
   waiting for someone to yell at me for this).

 - Add some cases to cover behavior fixed by previous commit.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@54413 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang