I was compiling mozilla-1.2a grabbed from mozilla's CVS server. It was giving errors about libIDL, saying that libIDL-config-2 reported version 0.8.0 but the library it found was 0.6.8. If I tried to compile it gave an error on IDL.h not found. The solution was to change the symlink /usr/lib/ libIDL.so to point to libIDL-2.so instead of libIDL-0.6.so.0.4.4. I know that mozilla-1.2a isn't in portage, but thought this might worth sorting out anyway. Does libIDL always come as part of ORBit? Could ORBit just depend on the separate libIDL instead? Hope this is helpful.
libIDL is for use with ORBit2 . in ORBit it was included and will remain so afaik. I'm assigning this to me, and closing as a reminder to self. thanks for the heads up :)