2006-04-23  Manish Singh  <yosh@gimp.org>

        * plug-ins/common/png.c: don't use long deprecated libpng API, and
        drop support for ancient libpng versions. Fixes bug #339402.

        * configure.in: use pkg-config to detect libpng. This means we now
        require at least libpng 1.2.2, but that's over four years old, so
        that shouldn't be that big a deal.