[Pharo-project] Hash changes, take 2

Hello, Here are the latest hash changes. It was easier for me to introduce basicIdentityHash on top of the changes I had done for scaledIdentityHash. I hope you don't mind. Also, note I had to change some senders of identityHash. Martin et al, would you mind reviewing these? After I wrote the code, I began feeling changing identityHash may not be what we want in general... Andres.