Remove a few more bogus returns when the switch covers all the enumerators.
Remove a few more bogus returns when the switch covers all the
enumerators.

Also remove a default that led to llvm_unreachable to make another
switch warn if any enumerators fail to be covered.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@130646 91177308-0d34-0410-b5e6-96231b3b80d8

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