Potential rejection of valid MaxMemFree and ThreadStackSize directives

trunk patch: https://svn.apache.org/r1542338

Submitted by: Mike Rumph <mike.rumph oracle.com>
Reviewed by: trawick, covener, sf


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1542549 13f79535-47bb-0310-9956-ffa450edef68