Why does toStringz return an immutable(char)*?

[Jonathan M Davis]

The main purpose of toStringz is to turn a string into a char* which can be 
passed to a C function. C doesn't have immutable, and I don't see any gain in 
having toStringz return an immutable(char)* rather than a const(char)*. Does 
anyone know why it returns an immutable rather than a const? What possible 
benefit does that have?

- Jonathan M Davis