First line should describe the file, not Guix

[McSinyx]

Hello Guix,

All Scheme source file in Guix starts with

> ;;; GNU Guix --- Functional package management for GNU

which is definitely the first thing one looks for right
after openning one.  For example, when I look into aa.scm,
I need to know whether it is for _ambiguous abbreviations_
or _any another_ stuff.

I suggest changing the first line into describing the source file,
which goes in hand with

> This file is part of GNU Guix.

Is there any reason against this that I'm not aware of?

Best regards,
McSinyx