Remove remaining mentions of libevent.
catch-app-errors: no need to use (handler-case (symbol-function ...) ...), use fboundp instead.
Fix no-overlap test on sbcl, add type checking for data argument of tcp-connect.
Fix write-sequence to tcp stream on sbcl.
Fix unclear errors when exiting event loop after some improperly failed tcp-connect calls.
Fix compiler warning in event.lisp.

Perhaps should remove 'activate' argument of add-event altogether?
Fix compiler warning and possible runtime problem in event-loop.lisp.

run-event-cb makes use of _evcb-err which is provided
lexically by catch-app-errors, so don't try to
compile run-event-cb outside catch-app-errors.
Fix tcp-connect-fail test.

Sometimes it gives 'timeout' and sometimes 'connection refused' error.
Merge pull request #106 from ivan4th/master

Assorted fixes, mostly for sbcl