Merge of r1850745,r1855446 from trunk:

modules/filters/config.m4: Make libxml2's inclusion of unicode/*.h files
a non-fatal warning/error under maintainer-mode.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1856931 13f79535-47bb-0310-9956-ffa450edef68