Remove outdated Clisp workarounds

The fixes seem to have been merged into Clisp in 2008.
Add :INTERACTIVE to restart to fix Clisp warning

The HyperSpec entry for RESTART-CASE and Clisp seem to disagree on the
need for :INTERACTIVE to make a restart interactively invokable.
Move stumpwm.lisp higher in the .asd

Now LOAD-RC-FILE is defined when loading user.lisp.
Fix use of changed, unexported clisp ffi function
Merge pull request #153 from jorams/fix-clisp

Fix Clisp, fixes #147