Rewrote all the toString and bit twiddling code in Integer and Long using

Rewrote all the toString and bit twiddling code in Integer and Long using
state-of-the-art recipes.  The resulting code is much faster than what it
replaced, as well as being more concise. While I was in the neighborhood
I also cleaned up a few other things in the boxed primitives (TYPE fields,
small-value caches, etc.).

Addressed review comments.