Convert assert(0) to llvm_unreachable to silence a warning about Addend being uninitialized in default case.
Convert assert(0) to llvm_unreachable to silence a warning about Addend being uninitialized in default case.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@211138 91177308-0d34-0410-b5e6-96231b3b80d8

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