Check ein:kernel-live-p in ein:ac-* functions
Make ein:jedi-complete work when kernel is dead

Previously deferred:callback-post was not called for the
deferred object from ein:jedi--completer-complete when the
kernel is dead.  It is called with an empty result now.
Fix compile warnings in ein-ac.el and ein-jedi.el
Do not try dot-complete when in string literal etc.