Why do "const inout" and "const inout shared" exist?

[Ola Fosheim Grøstad via Digitalmars-d]

I also think it would be a good idea for the D crowd to be 
specific when they compare to C++ const, which should be compared 
to D's shared version of const and not to the local variety.

C/C++ compilers provide other means to provide the optimizer with 
information about actual mutation/aliasing than const-types. So 
it doesn't really compare well.

Besides, none of this makes a lot of sense until you have fully 
specified a sound memory model + type system for shared...