cr_canseeotheruids(), cr_canseeothergids(): Man pages: Impacts of rename

When these functions were renamed 7 years ago, their man pages were not.
Rename the latter in accordance and fix the names inside them. Fix
references to them as well. Add the old man pages to the list of
obsolete files.

Reviewed by: mhorne
MFC after: 2 weeks
Sponsored by: Kumacom SAS
Differential Revision: https://reviews.freebsd.org/D40630

(cherry picked from commit c59ab75c04fa32bc6d292596ff5e4593a05a6b1b)