This is basically http://sourceforge.net/tracker/?func=detail&aid=3314388&group_id=5776&atid=105776. It seems the fix was simply removing the offending include. It probably could be observed in breaking media-plugins/gst-plugins-mplex, if not for the way gstreamer plugins are packaged in Gentoo. As such, simply a broken plugin gets installed.
+*mjpegtools-2.0.0-r3 (28 Sep 2012) + + 28 Sep 2012; Daniel Pielmeier <billie@gentoo.org> + +mjpegtools-2.0.0-r3.ebuild, + +files/mjpegtools-2.0.0-stream-params-include.patch: + Fix bug #436208. Thanks to Rafał Mużyło for the report.