libpng planned changes for etch

[Josselin Mouette <joss@debian.org>]

Here is a summary of the important changes I'm planning for libpng in
etch.

* Removal of the entire libpng source package: libpng2, libpng2-dev,
libpng10-0, libpng10-dev. All applications currently linking to libpng
1.0 will have to be rebuilt against libpng 1.2. As sarge's libpng
packages include symbol versioning, it can be done smoothly. Some
packages will temporarily depend indirectly on both versions, but they
shouldn't be broken.

* Removal of the libpng3 binary package, as only 2 packages in sarge
still depend on this one. Maybe we can keep it, though, as some
third-party binaries could require libpng.so.3.

* Removal of the libpng3-dev binary package, adding a Provides: in
libpng12-dev. I believe autobuilders can cope with such a change, as
they are already dealing with packages build-depending on libpng-dev,
which is a virtual package.

* Removal of the private symbols that are exported in the library. This
can break some applications directly using these private symbols. Which
means: it shouldn't happen, but you never know how software authors can
have stupid ideas.
-- 
 .''`.           Josselin Mouette        /\./\
: :' :           josselin.mouette@ens-lyon.org
`. `'                        joss@debian.org
   `-  Debian GNU/Linux -- The power of freedom