Patch for Word64

I was doing some work with Word64 and noticed that it was about 3 times slower than Int64. The reason appears to be expensive conversions from Int64# to Word64# and vice versa. I modified the libraries to remove the conversion overhead, and the result is that Int64# and Word64# now have equal performance, at least on the domain that I tested (==, +, -). I can't check into the tree, so I was told to send my changes to this list. Could someone else check them in? I have attached a patch file representing my changes. -Matt or [ricebowl, wearkilts, soysauce] on #haskell on Freenode