freeglut: add universal option

As requested in: http://librelist.com/browser//homebrew/2013/8/25/how-do-i-request-a-modfication-to-a-formula/
superenv: support PPC bottles

Allows for building bottles on PPC both with and without Altivec.
This is currently not active but will be enabled once superenv is
stable on Leopard.