Snow Leopard +universal necessity

[Ryan Schmidt]

On Snow Leopard, we build x86_64 by default. But there are some ports,  
e.g. wine, that cannot build 64-bit, so they force themselves to build  
32-bit instead. But that means all the dependencies must also be 32- 
bit, or 32-/64-bit universal. So it seems like it should probably be  
our recommendation to all Snow Leopard users to install all possible  
ports +universal for x86_64/i386, to avoid pain down the road when the  
user wants to install a port that happens to only be available as 32- 
bit. Most easily this could be accomplished by putting "+universal"  
into variants.conf. Maybe we should even do so in the default  
variants.conf on Snow Leopard.

Not installing dependencies universal causes issues like this:

http://trac.macports.org/ticket/20912