bug#21072: Brave new mark-defun (and a testing tool)

[npostavs]

npostavs@users.sourceforge.net writes:

> Glenn Morris <rgm@gnu.org> writes:
>
>> It seems this causes two python tests to fail.
>> See eg http://hydra.nixos.org/build/52829789
>
> It seems again to be an issue of different behaviour with
> transient-mark-mode disabled.

I've set the tests to use transient-mark-mode [1: ee54d2f4e4], we might
have to revisit the non transient-mark-mode behaviour though.

[1: ee54d2f4e4]: 2017-05-20 18:28:23 -0400
  ; Set transient-mark-mode to let mark-defun tests pass
  
http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=ee54d2f4e439b4a211c8fb7541ce22bac65bde8f