Offer lazy put and newFull

[treeowl]

I understand that these functions are designed to force values to make it easier to reason about what threads computations are performed on. But this is Haskell, and sometimes we want to do something subtle. Making users add datatype wrappers to avoid forcing their values just seems rude. I suggest lazyPut and lazyNewFull, but I don't care terribly much about the names.