Fixing namespace+prefix mode in Expat and removing optional fields from callbacks.

The first part is related to bug 6632:
  http://code.google.com/p/android/issues/detail?id=6632

I added these optional fields back when I was originally updating
the XML parser for Froyo. I've decided to remove them to simplify
migrating between Android and the RI. It should also save some
object allocations.

Note that the RI v5 and the RI v6 behave differently for optional
values on attributes; this motivated me to add the otherwise
unfortunate assertOneOf() method to the testcase. (We behave more
like RI v6, which is to supply the values upon request)

Change-Id: Icfa5d29976a86bf194b3ed7c0d9e2275c3bff9dd
4 files changed