Fix DDIV. Simplify DDIVU register loads. Implement DADDI, DADDIU. Fix XORI (wasn't copying top bits). Fix LWL/LWR.
Fix DDIV. Simplify DDIVU register loads. Implement DADDI, DADDIU. Fix XORI (wasn't copying top bits). Fix LWL/LWR.

hulkholden/n64js,beni55/n64js,beni55/n64js,matthewbauer/n64js,matthewbauer/n64js,hulkholden/n64js