swank:create-server no longer takes :coding-system

[chrnybo]

https://github.com/archimag/restas/blob/master/contrib/restas-daemon.lisp#LC363 wants to call swanks create-server with a key :coding-system, although that key disappeared in http://common-lisp.net/viewvc/slime/slime/swank.lisp?view=log#rev1.763