backport from trunk r1033519:

*) suEXEC: Add Suexec directive to disable suEXEC without renaming the
   binary (Suexec Off), or force startup failure if suEXEC is required
   but not supported (Suexec On).

Submitted by: trawick
Reviewed by: covener, wrowe


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1070639 13f79535-47bb-0310-9956-ffa450edef68