Apache Traffic Server - fixed installation on MacOS 10.8

I have fixed "trafficserver" formula, installation didn't work on MacOS 10.8.

Author of the patch is Dian Dwi Nugraha - http://blog.nugrahais.me/2013/01/28/troubleshooting-101-compiling-apache-traffic-server-on-osx-10-8-2-via-homebrew/.