- Properly support png 1.5
- Cleanup plist


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375467 35697150-7ecd-e111-bb59-0022644237b5
Properly support png 1.5

Obtained from:	Gentoo


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375468 35697150-7ecd-e111-bb59-0022644237b5
Properly support png 1.5

Obtained from:	pkgsrc


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375469 35697150-7ecd-e111-bb59-0022644237b5