libstagefright - Fix timestamp overflow

 - change time related variables to 64 bit to avoid overflow
 - composition time calculations were having overflow in
   SampleIterator and it propagates to the rest of the time
   related information for the frames

Change-Id: I035cbfaced1215eb1afd2c6cb900116e46006994
Merge "libstagefright - Fix timestamp overflow" into jb4.3