Maybe the doc strings for `mm-inlined-types' and
`mm-automatic-display' aren't so clear. Shouldn't
`mm-automatic-display' be mentioned in the doc string of
`mm-inlined-types' (or vice versa)?

I also added an entry for "x-emacs-lisp" in `mailcap-mime-data' in
mailcap.el (Not necessary for this but maybe reasonable?):