relay: ensure numeric options have numeric arguments
relay: ensure numeric options have numeric arguments

Issue #414 revealed that -m silently accepted a bogus option, leading to
undefined (faulty) behaviour.

Signed-off-by: Fabian Groffen <2c4829061e3ecacc1da315323749610b9ffaef65@gentoo.org>

grobian/carbon-c-relay,grobian/carbon-c-relay,grobian/carbon-c-relay