gst-ffmpeg: fix CVE issues

Backport patches to fix following CVE issues:

* CVE-2011-4352
* CVE-2014-7933
* CVE-2014-8542
* CVE-2014-8543
* CVE-2014-8544
* CVE-2014-8545
* CVE-2014-8546
* CVE-2014-8547
* CVE-2014-9318
* CVE-2014-9603

Patch for CVE-2014-9603 in upstream is applied for version 2.x. Becuase
source code changes, just partly backport part of the commit which is
applicable to version 0.10.13.

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>