Follow libx264 style to support "coder" option, and set it to
cabac by default.
Signed-off-by: Yi A Wang <yi.a.wang@intel.com>
Signed-off-by: Jun Zhao <jun.zhao@intel.com>
Reviewed-by: Steven Liu <lingjiujianke@gmail.com>
Signed-off-by: Mark Thompson <sw@jkqxz.net>