stagefright: Fix playback for mkv files with lacing

Most mkv files having 'lacing' in their audio section to save space.
Android did not handle this properly, sending all frames in the block
with the same time code, which causes stuttery playback.

Change-Id: I4dc76e7c2a53126c7fbdd3628fe7d339d2e3364e
Merge remote-tracking branch 'PA/kitkat' into kitkat-legacy