ports/172505: graphics/pngquant: Update to version 1.7.3

[araujo at FreeBSD.org]

Synopsis: graphics/pngquant: Update to version 1.7.3

Responsible-Changed-From-To: freebsd-ports-bugs->araujo
Responsible-Changed-By: araujo
Responsible-Changed-When: Tue Dec 11 13:03:42 UTC 2012
Responsible-Changed-Why: 
I'll take it.

http://www.freebsd.org/cgi/query-pr.cgi?pr=172505