Atlas update

[Vincent Habchi]

Hi Michael,

> Hi Vincent - With so many fixes / changes, once the updated Portfile is
> verified / fixed, my vote is to do the rev-bump. Makes future tickets
> easier to work with, among other things. - MLD

Noted.
By the way, I figured out it is not very wise to change the default compiler from macports-clang-3.3 to XCode-clang, since a lot of people out here run Atlas on old machine that have not the last Xcode installed. 

So I’m going to make it conditional. For the people that have Xcode 5 installed, clang Xcode is going to be the default, but it will be macports-clang-3.4 for the others.

Now, does some guru out there remember me how to test against Xcode version?

Thanks,
Vincent