Mavericks port

Piotr, before you release, can you merge in my fixes to 

PyIlmBase/PyImath/PyImathM44Array.cpp

and 

PyIlmBase/PyImath/PyImathMatrix44.cpp

This will fix an issue on OSX and on Windows that prevents correct compilation. I am surprised these haven't shown up before.

Please disregard the rest of the build system stuff, I want to chat with you about it first.