pf scrub max-mss checks

[Gregory Steuck <greg@nest.cx>]

Hello,

Do you guys think it would be prudent to check the value for max-mss in
scrub rules? It bit me today when I accidentally specified a value over
2^16 and it was silently cast to a 16 bit value. Kind of violates the
principle of least surprise.

I can supply a patch if it would be a better explanation of what I mean.

Thanks
Greg