Default hashing function for AA's

[RazvanN]

Hi all,

We in the UPB dlang group have been having discussions about the 
hashing functions of associative arrays. In particular, we were 
wondering why is the AA implementation in druntime is not using 
the hash function implemented in 
druntime/src/core/internal/hash.hashOf for classes that don't 
define toHash().

For us, that seems to be a very good default hashing function.

Best regards,
On behalf of the UPB Dlang group