As of (From the CLISP src/Changelog):
2006-10-05 Sam Steingold sds@podval.org
merged LOOKUP-FOREIGN-FUNCTION & FOREIGN-LIBRARY-FUNCTION into FIND-FOREIGN-FUNCTION; LOOKUP-FOREIGN-VARIABLE & FOREIGN-LIBRARY-VARIABLE into FIND-FOREIGN-VARIABLE ...
This includes CVS releases starting with clisp-2.41.
FFI::FOREIGN-LIBRARY-FUNCTION and FFI::FOREIGN-LIBRARY-VARIABLE have effectively been made legasy.
In the current CVS head (but not the last clisp-2.44.1 release) these functions have quietly disappeared. This causes problems with the CLISP CVS head in cffi-clisp.lisp.
I'm not sure what version of CLISP need to be supported. Should the new FFI::FIND-FOREIGN-FUNCTION and FFI::FIND-FOREIGN-VARIABLE interface now be used.