Properly support png 1.5

Obtained from:	Gentoo


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375456 35697150-7ecd-e111-bb59-0022644237b5
Properly support png 1.5

Obtained from:	Gentoo


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375457 35697150-7ecd-e111-bb59-0022644237b5
Properly support png 1.5

Obtained from:	Gentoo


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375458 35697150-7ecd-e111-bb59-0022644237b5
Properly support png 1.5

Obtained from:	Archlinux


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375459 35697150-7ecd-e111-bb59-0022644237b5
Properly support png 1.5


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@375460 35697150-7ecd-e111-bb59-0022644237b5