Allow either a _d or a non _d library for debug builds.

This allows a debug PySide to be built with a non-debug Python.
Set CMAKE_OSX_ARCHITECTURES.
Fix ALTERNATIVE_QT_INCLUDE_DIR
Add the OSX specific flags for Shiboken too.
Add --osx-arch option so the desired build architecture can be specified
Merge pull request #16 from RobinD42/more-tweaks

More tweaks