Merge r1809135 from trunk:

On the trunk:

mpm_common.h: guarding AP_ENABLE_EXCEPTION_HOOK against use when undefined so that -Wundef does not triggger.




git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1838052 13f79535-47bb-0310-9956-ffa450edef68