This also resolves some typing issues that only 'accidentally' worked, like declaring
a function to return type A, and the definition actually returning type B (which works
if type B is a subtype of type A). I like to call these "ninja imports".
To prevent problems like this in the future, I put all globals in a HackStudio.h.
I'm not sure about the name, but main.h and common.h felt wrong.
