[PATCH] configure: check that the version of emacs we may have is at least 24

[David Bremner]

Tomi Ollila <tomi.ollila at iki.fi> writes:

> This also effectively drops support to Emacs version 23, which was
> deprecated in version 0.23.2 (2016-11-20) and did not entirely work
> any more.

Pushed.

d