message: Remove warning about switch fall-throughs
diff: @@ -219,6 +219,7 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
  AX_CHECK_COMPILE_FLAG([-Wextra],[CXXFLAGS="$CXXFLAGS -Wextra"],,[[$CXXFLAG_WERROR]])
  AX_CHECK_COMPILE_FLAG([-Wformat],[CXXFLAGS="$CXXFLAGS -Wformat"],,[[$CXXFLAG_WERROR]])
  AX_CHECK_COMPILE_FLAG([-Wformat-security],[CXXFLAGS="$CXXFLAGS -Wformat-security"],,[[$CXXFLAG_WERROR]])
  + AX_CHECK_COMPILE_FLAG([-Wno-implicit-fallthrough],[CXXFLAGS="$CXXFLAGS -Wno-implicit-fallthrough"],,[[$CXXFLAG_WERROR]])
  ## Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
  ## unknown options if any other warning is produced. Test the -Wfoo case, and
  