rtmpdump: security bump to current HEAD

Fixes:

- CVE-2015-8271: The AMF3CD_AddProp function in amf.c in RTMPDump 2.4 allows
  remote RTMP Media servers to execute arbitrary code
  https://www.talosintelligence.com/reports/TALOS-2016-0067/

- CVE-2015-8272: RTMPDump 2.4 allows remote attackers to trigger a denial of
  service (NULL pointer dereference and process crash).
  https://www.talosintelligence.com/reports/TALOS-2016-0068/



Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>