Backport r655711

When group is given as a numeric gid, validate it by looking up the
actual group name such that the name can be used in log entries.

PR: 7862
Submitted by: <y-koga apache.or.jp>, Leif W <warp-9.9 usa.net>
Reviewed by: fielding, jim, rpluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@660756 13f79535-47bb-0310-9956-ffa450edef68