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>
(cherry picked from commit 4ebd2fa277fdffecca146d07c78954653517eff4)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rtmpdump/rtmpdump.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-RTMPDUMP_VERSION = a107cef9b392616dff54fabfd37f985ee2190a6f
+RTMPDUMP_VERSION = fa8646daeb19dfd12c181f7d19de708d623704c0
 RTMPDUMP_SITE = git://git.ffmpeg.org/rtmpdump
 RTMPDUMP_INSTALL_STAGING = YES
 # Note that rtmpdump is GPLv2 but librtmp has its own license and since we only