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

[Eli Zaretskii]

> Date: Mon, 20 Apr 2015 20:41:26 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> Cc: 20325@debbugs.gnu.org
> 
> I don't care what format is used, and it's fine with me to revert my attempt 
> to 
> bring order to this little corner of chaos.  Another possibility is to modify 
> CONTRIBUTE to add "Fixes: debbugs:NNNNN" and "Fixes: bug#NNNNN" and etc. as 
> alternative ways to spell "Bug#NNNNN".  It's no big deal either way.

Indeed.  But please, let's decide soon, and make that decision hold
for at least a year.