[gentoo-science] new blas infrastructure and prefix

Hi all,

So I was looking at the science overlay from my prefix on OS X.
And portage wanted me to upgrade my blas/cblas/lapack stack to the
new structure. I know they are marked ~x86 and ~amd64 but it doesn't
look good considering that I had a working stack in my prefix before.

So I may make things a little more prefix friendly (OS X in particular)
in the coming days. I am also thinking of adding an ebuild to use the
native vectorize framework on OS X, unless someone strongly objects to it.

Francois