After emerging expat with ACCEPT_KEYWORDS="~amd64", kdeinit was broken and mozilla-thunderbird-1.5-r3 would not compile. Vlc may also be affected.
Remerging the previously installed version of expat solved all these problems.
*** This bug has been marked as a duplicate of 128069 ***
# revdep-rebuild -p --library libexpat.so.0
# revdep-rebuild --library libexpat.so.0
It is not actually simple, because Opera needs libexpat.so.0 too
I resolved it buy making symlink libexpat.so.0 -> libexpat.so. Maybe ebuild should create this link too?