I updated the existing ebuild for vesion 2.29 to the latest release (2.31). I removed the patch used for the 2.29 ebuild, as it seems the changes have been incorporated in the upstream source code now. I tested it locally on AMD64 with GCC 4.2. The test suite seems to fail on some different cases though (as documented in the ebuild) but I have not looked into the reason why. The previous version didn't pass the complete test suite either, so that shouldn't be a problem.
Created attachment 131766 [details] ns-2.31.ebuild
I also tested on x86 and there it passes the complete test suite. So it appears any problems are related to amd64 and possible other architectures (which I haven't tested).
Thanks, in CVS.