Some fixes around `delete-other-frames' and `next-frame'

Some fixes around `delete-other-frames' and `next-frame'

* src/frame.c (Fdelete_frame): Clarify doc-string.
* lisp/frame.el (delete-other-frames): Delete other frames on
FRAME's terminal instead of the current terminal.  Delete
non-minibuffer-only surrogate frames too.  See
http://lists.gnu.org/archive/html/emacs-devel/2016-08/msg00467.html
* doc/lispref/frames.texi (Deleting Frames): Minor fixes for
docs of `delete-frame' and `frame-live-p'.  Add entry for
`delete-other-frames'.
(Finding All Frames): Fix doc of `next-frame'.