[new AA] aaLiteral compiler support

This is a dmd part of the new AA implementation. 
This PR depends on D-Programming-Language/druntime#1046 and uses new aaLiteral version (with arrays of keys and arguments)

So it's a forward reference problem?  If you need to access members of `AssociativeArrayHandle` you're either going to have to defer handling other declarations until you see it, or put in some casts to avoid knowing the type. (ie treat it as a `void*[N]` and cast to the correct function pointer type)