Unreviewed. Add missing sections to documentation.

* UIProcess/API/gtk/docs/webkit2gtk-docs.sgml: Add
WebKitUserContent and WebKitUserContentManager sections to the
documentation.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@171914 268f45cc-cd09-0410-ab3c-d52691b4dbfc