ghc-in-ghci memory usage

I just tried using the ghc-in-ghci script again and it appears that the memory usage problems have been resolved. Probably thanks to Simon Marlow who fixed a lot of space leaks in ghc. A reminder of how to use it: ./utils/ghc-in-ghci/run.sh -j<n> will load ghc into ghci so you can `:r` to recompile when you make a change. Cheers, Matt