Small change to 'ps'

[Sheldon Givens]

Hello everyone,

It occurs to me that FreeBSD ps lacks the ability to disable header. This
seems like a really obvious feature, and I may have simply missed it's
existence (despite my relentlessly searching the man page) but here is a
small patch that sets the flag 'n' to disable header output.

Diff from CURRENT:
http://sigsegv.ca/sheldon/ps.c-diff
http://sigsegv.ca/sheldon/ps.1-diff

Happy New Year, everyone!