Replace client pointers with references

References should be used when NULL is not necessary, but if there is a possibility of a NULL value, pointers should be used.

Also, in server functions, the stupid conversions from client to cn and back should be removed.

This might take a while to complete, and it will definitely mess up the ability to merge c++11/vectBackEnd even more.

Github didn't allow me to reopen pull request #9, even if I reset master to the commit before pull requst #10.