Bug#819779: gdk-pixbuf: libgdk-pixbuf2.0-dev depends on libpng-dev but gdk-pixbuf2.0.pc requires libpng12-dev

[peter green]

>
> * ships a gdk-pixbuf2.0.pc that requires libpng12.pc;
> * depends on libpng-dev which:
>    - on experimental, is a real package that does not ship libpng12.pc
>      but only libpng16.pc and libpng.pc;
>    - on unstable, is provided by libpng12-dev which does provide
>      libpng12.pc, but that situation should change to that of
>      experimental whenever the new libpng-dev real package is uploaded to
>      it.
The situation has now changed but we still have a problem.

gdk-pixbuf2.0.pc now requires libpng16.pc but the dependency is still on 
libpng-dev which is available both as a real package and as a provides 
from libpng12-dev. So depending on which option is selected in 
satisfying the dependencies the system can end up with a broken 
gdk-pixbuf2.0.pc

I belive the correct thing to do is to depend on libpng-dev (>=  1.6), 
libpng-dev (<<  1.7).

libpng developers, any thoughts on this?