CIRCLE WITH A DOT

@gsuberland @uecker I won’t defend Clang’s naming choices in every case, but I believe this specific one is all GCC; Clang originally called this -Wc++0x-narrowing (eventually -Wc++11-narrowing) and only added the -Wnarrowing alias for GCC compatibility. In any case, the documentation should really suggest -Wconversion, and on that front I can definitely accept blame for Clang, because our warning group documentation is awful