suexec: Pass the SERVER_SIGNATURE envvar through to CGIs.

Submitted by: Zvi Har'El <rl math.technion.ac.il>
Reviewed by:  Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@104703 13f79535-47bb-0310-9956-ffa450edef68