CLISP doesn't know :UTF-8 external format

quri and dependent libraries now fail on CLISP due to the :UTF-8 usage:
http://cl-test-grid.appspot.com/blob?key=16617jgw5i

I suggest to change to `#+clisp 'charset:utf-8 #-clisp :utf8`

CLISP docs: http://www.clisp.org/impnotes/encoding.html