There is a new release of javacup. Please update portage.
Created attachment 440692 [details] javacup-0.11b_p20160615.ebuild
Created attachment 440694 [details, diff] javacup-ebuild.patch
Created attachment 440696 [details, diff] javacup-0.11b_beta20160615-build-xml-svn.patch
If someone gets to this before me, be very careful. The cyclic dependency on jflex and the unstable ABI make this package very problematic.