Non-transitive immutable? Read only struct.

[Ola Fosheim Grøstad]

I guess I should have stated more clearly to major optimization 
advantages of having more memory set as immutable:

1. It allows the compiler to assume that there is no aliasing.

2. It allows the compiler to retain loaded values 
(registers/stack) even accross invalidation/barriers.

3. It allows generic code to retain cached copies of 
values/pointers obtained through a chain of immutable. Including 
pointers to mutable memory.