1) Move the attachment structures into the encrypted message body.
2) Encrypt attachments with symmetric keys transmitted in the
encryptd attachment pointer structure.
3) Correctly handle asynchronous decryption and categorization of
encrypted push messages.
TODO: Correct notification process and network/interruption
retries.
The code we use for PDU parsing and composing comes straight from
the Android framework, but it's an internal API, so we duplicate
the code here. These changes represent updates that have been
made as of the JB release.
