core.xml: Clarify the Location and LocationMatch directive doc to emphasize

restrictions on valid configuration values.

PR: 45987
Submitted by: Dan Poirier
Reviewed by: Paul J. Reder



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@726882 13f79535-47bb-0310-9956-ffa450edef68