Merge from origin/emacs-26

0860ac0 (origin/emacs-26) Improve documentation of features that use ...
fae1ff6 Fix docstrings in pong
82a2894 Improve doc strings of 'append-to-buffer' and friends
cb0403d Fix octave-mode ElDoc support
691790b Avoid Groff hanging on MS-Windows when invoked by "M-x man"

diff --cc doc/emacs/display.texi
Simple merge

diff --cc lisp/man.el
Simple merge

diff --cc lisp/play/pong.el
Simple merge

diff --cc lisp/progmodes/octave.el
Simple merge

diff --cc lisp/simple.el
Simple merge