mod_xml2enc not available
mod_xml2enc is not available in package repositories. apache2 now starts without it (see #1376002) but you still get the following warning:
[Wed Dec 24 13:35:57.142324 2014] [proxy_html:notice] [pid 7028:tid 140101697644416] AH01425: I18n support in mod_proxy_html requires mod_xml2enc. Without it, non-ASCII characters in proxied pages are likely to display incorrectly.
Googling around, it seems people are still building this module from source.