[Issue 18921] make core.internal.hash cater to memberwise hash chaining

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18921

github-bugzilla at puremagic.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--