bug#20325: convert "fixes:debbugs:123" in log to (Bug#123) in ChangeLog

[Eli Zaretskii]

> Date: Sat, 18 Apr 2015 01:44:59 +0300
> From: Dmitry Gutov <dgutov@yandex.ru>
> Cc: 20325@debbugs.gnu.org, Paul Eggert <eggert@cs.ucla.edu>
> 
> We've used the debbugs:1234 format in commit messages for a while
> now.

For some value of "we".  CONTRIBUTE still requires to use
"Fixes: bug#NNNN", and that's what I've switched to once those
requirements were written.  Which was already a change from the
previous procedure, which preferred simply "Bug#NNNN".

I wish you guys settle on something once and for all, never mind what,
and stop bikeshedding about it and changing the procedures every 2
weeks or so.