bug#14480: A few error to user-error replacements

[Kelly Dean]

A couple more: in emacs-24.3/lisp/emacs-lisp/lisp.el, the calls to error on 
lines 187 and 618 should be calls to user-error. Can't say current line numbers 
in trunk, since they'll probably change by the time somebody reads this, and 
can't provide context via diff since the FSF requested that I not send any more 
patches
(see http://debbugs.gnu.org/cgi/bugreport.cgi?bug=14492).

Reporting these minor things in prose seems not worth the effort. Should users 
even be reporting them? Or is some computer-assisted error->user-error bulk 
conversion going to take place, and reporting individual ones is unnecessary?