Places we should use the new ByteBuffer intrinsics

[Andrew Haley]

We discussed where we should be using the new Unsafe unaligned
intrinsics.

I found these:

	ByteBufferAs$Type$Buffer.  These use slow bytewise accesses,
	and should be converted.

        DirectByteBuffer.  This probes for unaligned memory support
        and uses byte-by-byte accesses if it isn't available.  We
        should probably convert it after doing some performance
        measurements.

        sun.security.provider.ByteArrayAccess.  This uses a lot of
        hand-carved custom code to handle data which largely
        duplicates that now in Unsafe, but big-endian platforms (and
        little-endian ones which don't support unaligned accesses)
        always use byte-by-byte accesses for unaligned data.  Again,
        we should probably convert it after doing some performance
        measurements.

Andrew.