Merge from origin/emacs-25

bf21c84 Fix quoting problem in cc-engine debug message
8f36614 Add electric-quote-string unit test
6280531 Don’t electrically quote ‘'’ in Python
fd7b430 `nreverse' Grep hits before passing them to xref--convert-hits

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

diff --cc test/lisp/electric-tests.el
Simple merge