Fix a bunch of javac -Xlint warnings in our code.

I think "fallthrough" uncovered a couple of real bugs in the kxml code, but
other than that there's nothing very exciting here. This addresses all but
one of the non-xml warnings. I'm assuming that we'll move the xml cruft out
into external at some point (since we're deliberately not maintaining it).

Change-Id: Ice81253b019df7b19d6557e719663b7bdc11fb22
27 files changed