[oe] Boost version

[Philip Balister]

I'd like to remove the DEFAULT_PREFERENCE = "-1" from the boost recipes 
so we are using the latest boost.

Currently, I am checking the packages that use boost I care about, such 
as gnuradio.

Does anyone else care what version of boost is the default?

Also, the boost-1.41 recipe is based of the cmake branch of boost. How 
well maintained is this? It has been two months since boost-1.42 was 
released and there is not corresponding cmake version.

Philip