sim: replacing ChangeLog files with online git logs

[Eli Zaretskii]

> Date: Mon, 22 Mar 2021 03:19:10 +0100 (CET)
> From: "Maciej W. Rozycki" <macro@orcam.me.uk>
> cc: Andrew Burgess <andrew.burgess@embecosm.com>, gdb@sourceware.org
> 
>  For the record the glibc project has a way to automatically produce 
> ChangeLog from commits at release time.  This may be something to look 
> into if useful.

That's the other script in Gnulib that was mentioned in this
discussion.  Someone said it cannot support our codebase well enough.