Bug#650601: transition: libpng 1.5

[Tobias Frost <tobi@debian.org>]

Hi,

Now the stats read: 
Built: 417
Failed: 112
OK: 304

To get forward, I drafted some MBF announcement on the Titanpad. Would
be cool if some can check it and maybe improve it (writing is not my
strength)

https://titanpad.com/libpng16-transistion

In the draft propose the following plan:

0. Assess situation (rebuld) -- done
1. MBF announcement 
2.  File bugs
for packages failing to build or needing updates in the B-Ds
2. Upload
libpng1.6 to unstable, providing libpng-dev (after "GO" from the
release team)
2a Upload libpng1.2 without providing libpng-dev to
unstable
3. Raise severity to RC
4. Prepare patches and NMU them
5. binNMU
6. fix remaining issues to finish transition
7. Remove libpng12 from
unstable

I'd go to upload 16 package with providing libpng-dev from day 1. and
then in a second step (as it needs to pass NEW) provide libpng-dev as
real package to allow versioned depends later. This second-step package
can be cleared via experimental. 

Nobuhiro, what do you think? As said, now I'd have time 
Emilio/Release-Team: The plan sounds OK with you?