building master against mac 10.7.4 using the 10.6 SDK

[Tor Lillqvist]

> * Neither is building against something else than the 10.4SDK
> something that has been tested

It *has* been tested to build against the 10.6 SDK, using clang from
Xcode 4.3, and it (now) works fine as far as I could see. Yes, I know
that such a build is not to be distributed, at least not without big
warning signs that it won't run on 10.4 or 10.5, etc etc.

> * and even less so is creating a 64bit build on Mac.

That is true indeed.

--tml