m4v_h263: Fix heap buffer overflow issue in BitstreamFillCache

Check for bitstream buffer overflow in PVLocateM4VFrameBoundary
and PVSearchH263FrameBoundary

Bug: 154058264
Bug: 136173360
Test: POC in bug description

Change-Id: Ied65243a13dc9923e6b9433b5b625db6f8b28556
(cherry picked from commit 502b917de8d94a652c75adb0ca7d6644698f46d6)
2 files changed