Merge from emacs-26

Merge from emacs-26

55c9bb9f3c Fix comint-get-old-input-default for output field case (Bu...
26819cd1c0 ; ChangeLog.3: Fix typo.
e35a08ea4b Prevent infloop in 'delete-trailing-whitespace'

* lisp/progmodes/cperl-mode.el:
* lisp/progmodes/cc-engine.el:
* lisp/progmodes/cc-mode.el: Fix tabs mixed with space preventing
commit hook from succeeding.