LibAAH_RTP: Fix a deserialization bug. DO NOT MERGE

Fix for bug 6446715

Fix a deserialization bug which was causing an assertion failure in
stagefright and bringing down the entire media server.  Basically, you
will hit this any time you play a track longer than ~2147 seconds.
(Technically, the crash will happen any time the play pointer at a
 position which is ~2147 * (1 * 2N) where N >= 0)

Change-Id: Ic0d371b0f6c29fddf0a033f5de08a70b3e63c854