Lots more bounds-checking/exception-throwing consistency.

Overflow-safe checks all round, plus better detail messages. This isn't
quite everything, but it's a large chunk of the work. Most notably, this
is all of io and nio.

There are numerous changes of exception priority here, and the harmony
tests noticed a subset of them in the nio code. I've modified our checked-out
copy of the tests to accept any of the throwable exceptions.

Change-Id: Id185f1228fb9a1d5fc9494e78375b5623fb0fe14