Merge r1884505, r1915625 from trunk:

Merge r1884505, r1915625 from trunk:

The Microsoft OOXML format uses xml packaged into a zip file, and has
mimetypes like:

application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

This mimetypes contains 'xml', but is unfortunately not an xml file.

xml2enc processes these files (in particular, when mod_proxy_html is
used), typically resulting in them being corrupted as it seems to
attempt to perform a ISO-8859-1 to UTF-8 conversion on them.

* modules/filters/mod_xml2enc.c (xml2enc_ffunc): Restrict test for XML
  types to matching "+xml".

Submitted by: Joseph Heenan <joseph.heenan fintechlabs.io>, jorton
PR: 64339
Reviewed by: jorton, ylavic, gbechis
Github: closes #410

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1916412 13f79535-47bb-0310-9956-ffa450edef68