./configure say error with libpng when compile tvtime on FreeBSD

[Xavier xfm]

Hi to all,

I try to compile tvtime ( http://tvtime.net/ ) on 9.0-RELEASE

I copy the log error to: http://pastebin.com/h40fa1s4

./configure say error with libpng, but I installed libpng-1.5.9 from source
code well on this machine 9.0-RELEASE

Somebody can help me to compile tvtime on 9.0-RELEASE ?

Thanks.