Finally I've found a way how to force McCLIM to partially accept non-ASCII input when used with SBCL. For each of the non-ASCII CHARACTERs to be input by the key CODE the following actions must be done:

(xlib:define-keysym CHARACTER (xlib:keysym CODE)) (in-package :goatee) (add-gesture-command-to-table CHARACTER 'insert-character *simple-area-gesture-table*)

It is not a perfect solution, because dead keys are ignored.

Milan Zamazal