Merge from origin/emacs-25

d1efbaf Fix documentation of completion functions
65c96cc Clarify documentation of 'font-lock-maximum-decoration'
2ad3d01 * doc/misc/cl.texi (Usage): Add some more details.
b49cb0a Fbackward_prefix_chars: stay within buffer bounds

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

diff --cc doc/lispref/minibuf.texi
Simple merge

diff --cc src/syntax.c
Simple merge