Add recognition of the GNU/Hurd kernel platform.

Submitted by:	Adam Farrell <skate111@stampede.org>
Reviewed by:	Ken Coar


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@84993 13f79535-47bb-0310-9956-ffa450edef68