Implementing multiple inheritance in D

[kenji hara]

I have tried to implement multiple inheritance in D.

My first idea is binary inheritance tree with using alias this, but
current dmd doesn't look alias this on superclasses.
So I have tried to fix this behavior.
-> https://github.com/9rnsr/dmd/tree/MultiInheritPatch

Result:
-> http://ideone.com/iD4JE

Some issues:
- Calling constructors of superclasses syntax.
- Object layout (share __monitor object? reduce overhead?)

Do you think?