ps: add build option to disable ps option warning

ps: add build option to disable ps option warning

Slackware seems to have this patch, while it is not in use(?) Well,
the upstream procps-ng allows one to disable warnings if that is
wanted. After all having this sort of 'feature' does not cost much,
while lacking it might annoy someone.

A patch from Slackware.

Reference: http://www.ftp.be/packages/slackware/slackware_source/a/procps/procps.nowarning.diff.gz
Backported-by: Sami Kerola <kerolasa@iki.fi>
Conflicts:

	proc/ksym.c