Toolchain tweaks

Playing with meta-mingw, it was clear that there were some simple changes we could make to the core that would improve things for non-linux SDKs. This series includes those changes. Since I like pain, I also attempted a darwin build and have included some tweaks for that too.

When looking at the gcc recipes, it also became clear that we have way too many include files and the whole thing was a bit of a maze. The series has some changes in to combine various files together and simplify things.

I appreciate this may complicate moving things into meta-oe such as gcc 4.7. I would propose when we do that, we put them into recipes-gcc-<version> and include a snapshot of the .inc files at that time. The alternative is the continual copy and paste growth of the .bb files (libgcc being a more extreme example) which I don't think lends itself to future maintenance of the recipes.

There are some layers which for example use gcc-cross4.inc, they should just be able to switch directly to gcc-cross.inc. I think this applies to meta-arago-extras.

This also leads the way to possibly further unify and clean up some of the configuration (e.g. the do_configure_prepends) but I will leave that for another series when someone has some further time to spend on it.

Cheers,

Richard