gnatgcc moving from gnat to gnat-x.y

[Nicolas Boulenguez <nicolas.boulenguez@free.fr>]

Hello.  Unless someone objects, I intend to upload to unstable:

gnat-4.6 4.6.4-2
* includes the /usr/bin/gnatgcc->gnat-x.y symbolic link, which is
  useful without the default compiler.
* Conflicts and Replaces: gnat (<< 4.6.1) accordingly
* includes the /usr/bin/gnatgcc and debian_packaging.mk Makefile
  snippet, which is not limited to libraries.
* Conflicts and Replaces: dh-ada-library (<< 5.10) accordingly.

gnat 4.6.2
* stops including /usr/bin/gnatgcc
* Depends: gnat-4.6 (no version)

dh-ada-library 5.10:
* stops including debian_packaging.mk
* warns in README.Debian that the snippet has moved to gnat-4.6>=4.6.4-2.
  A dependency would make the main executable unusable with gnat-4.9.

I intend to skip gnat-4.8 unless someone complains.  Next gnat-4.9
upload will contain gnatgcc and debian_packaging.mk.  All this is in
the monotone database, only needing update of some versions.