Merge r1399413 from trunk:

Export mod_xml2enc.h so that others can use the module.

Submitted by: minfrin
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1400961 13f79535-47bb-0310-9956-ffa450edef68