Bug#2342: libpng too old (0.71) for Arena

[Helmut Geyer <Helmut.Geyer@IWR.Uni-Heidelberg.De>]

Package: libgr
Version: 2.0.5-3

Arena needs at least the 0.87 png library to work correctly with
interlaced PNG images. The current version is 0.88. Until this changes
arena will be linked to a static libpng library.

	Helmut