bug#3302: Frame deletion with 'force fails

[David Reitter]

In an Emacs -Q (recent CVS, NS port), doing the following right after  
startup:

  (delete-frame (selected-frame) t)

will lead to an "Attempt to delete the only frame" error.  This seems  
needless in non-X/non-Windows environments.

frame.c, delete_frame():
  /* x_connection_closed must have set FORCE to `noelisp' in order
     to delete the last frame, if it is gone.  */
  if (NILP (XCDR (Vframe_list)) && !EQ (force, Qnoelisp))
    error ("Attempt to delete the only frame");

If there are technical reasons for this, it would be good if the doc  
string for `delete-frame' was updated.