Update libsrtp to upstream commit be95365fbb4788b688cab7af61c65b7989055fb4

This CL updates libsrtp 1.5.x to the latest upstream commit in the
"1_5_x_throttle" branch.

Notable changes:
- Increase maximum tag length to 16 bytes to allow for GCM cipher suite.
- Prevent potential DoS attack due to lack of bounds checking on RTP header
  CSRC count and extension header length. Credit goes to Randell Jesup and
  the Firefox team for reporting this issue.

R=juberti@chromium.org

Review URL: https://codereview.chromium.org/1434033004 .
6 files changed