tree-wide: do not print hint about -M if -M is already used

tree-wide: do not print hint about -M if -M is already used

(Or when -H is used, since -H and -M are incompatible.)

Note that the slightly unusual form with separate boolean variables (hint_vars,
hint_addr) instead of e.g. a const char* variable to hold the message, because this
way we don't trigger the warning about non-literal format.