As per bug #203886 and due to some arches lacking good ocamlopt support(ie, ocaml native code compiler), it was decided to make it optional so that it can be use masked on arches where it causes problems. I'll attach a diff against mediawiki 1.11.0 ebuild.
Created attachment 140405 [details, diff] allow not having ocamlopt patch, enabled by default
http://overlays.gentoo.org/svn/proj/webapps/migration/www-apps/mediawiki/ Will be in CVS for Bug 207757.
fixed