libpng 1.5.0 has issues and is breaking builds

[Robert Goldman]

I had a crash when trying

port install graphviz

if that helps.  I'm afraid I am not a sophisticated enough user to
provide a more helpful bug report.  But someone who is more
sophisticated might try this build and be able to generate a useful report.

The crash left my ports in an odd state, too.  I got the updated libpng,
but some systems (notably texlive) that depend on it no longer work,
probably because the port invocation got interrupted.

HtH,
r