twolame-0.3.10 installs: /usr/share/doc/twolame: api.txt html psycho.txt vbr.txt /usr/share/doc/twolame-0.3.10: AUTHORS.bz2 ChangeLog.bz2 README.bz2 TODO.bz2 configure --docdir does not seem to be used by doc/Makefile.am. Here's a patch for doc/Makefile.am (I did post this upstream a while ago with no response: http://sourceforge.net/tracker/index.php?func=detail&aid=1709609&group_id=136040&atid=735435 ) and a patch for the ebuild.
Created attachment 128065 [details, diff] twolame-0.3.10-docdir.patch
Created attachment 128067 [details, diff] patch ebuild to use twolame-0.3.10-docdir.patch
fixed it inside ebuild, we'll see what next upstream version brings us and change the ebuild accordingly.