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

[Walter Bright via Digitalmars-d]

On 7/1/2017 3:12 PM, Timon Gehr wrote:
> It used to be the case that const(inout(T)) = const(T),

Anyone want to run git bisect and see when this changed? This would help in 
figuring out the rationale.

Here's the code to test with it:

inout(const char)* foo(inout(const(char))* p)
{
     pragma(msg, typeof(p));
     static assert(is(typeof(p) == const(char)*));
     return p;
}