kill a FIXME in IsIntegralPromotion
kill a FIXME in IsIntegralPromotion

IsIntegralPromotion should consider the signedness of FromType when
calculating promotions. This, as of now, cannot be exercised on any
platform so there is no corresponding test.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@135803 91177308-0d34-0410-b5e6-96231b3b80d8

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