Update bundled libpng to v1.2.16. git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@5666 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Update ZLIB to 1.2.1. git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@3809 ea41ed52-d2ee-0310-a9c1-e6b18d33e121