Add LLVM_FALLTHROUGH annotation to case statement that intentionally falls through to next case stmt to silence -Wimplicit-fallthrough clang warning.
Add LLVM_FALLTHROUGH annotation to case statement that
intentionally falls through to next case stmt to silence
-Wimplicit-fallthrough clang warning.

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb