Get all process characteristics on FreeBSD: Redmine #1947

Update ps options to get control over all process characteristics on FreeBSD systems.

Checked against the test case provided in https://cfengine.com/dev/issues/1947, and from my own tests. (FreeBSD 9.1, 8.2, 7.4)

I would like to wait for Igor feedback, in the meanwhile I will also update ps options for NetBSD and OpenBSD in the same PR, it wouldn't be too difficult