plt/racket — pull request #339 by m4burns (2013-05-13 01:52:04+00:00)
Title: Use libpng 1.6.x if 1.5.x can't be found

libpng 1.6.x has superseded 1.5.x on (at least) Archlinux. This change
adds libpng16.so to the set of names tried when looking for the system
libpng.