add x264(+Yasm) as dep in ffmpeg easyconfig

{chem}[intel/2015b] CHARMM 37b2 (REVIEW)

{bio}[intel2015b] Sailfish 0.7.4 (REVIEW)

{data} [intel-2014b] MySQLdb 1.2.5 Python 2.7.8 (REVIEW)

{lib} [intel-2014b] lxml 3.4.2 (REVIEW) 

{vis}[intel/2015b] animation 2.4 (R v3.2.1) + GraphicsMagick 1.3.21 + ffmpeg 2.8 (WIP)

{vis} [intel-2014b] PyQt 4.11.4 (REVIEW)

{lang}[intel/2015b] Python 3.5.0 + several pkgs on top of it (WIP)

{vis} [intel-2015a] Mesa 10.5.5 (REVIEW) 

{tools}[dummy] Aspera Connect 3.6.1 (REVIEW)

{numlib}[intel/2015b] Hypre 2.10.1 (REVIEW)