h264dec: support gaps between pictures.

Signed-off-by: Zhong Cong <congx.zhong@intel.com>
ih264dec: support gaps between pictures 2.

Signed-off-by: Zhong Cong <congx.zhong@intel.com>
h264dec: support gaps between pictures 3.

Signed-off-by: Zhong Cong <congx.zhong@intel.com>
h264dec: support gaps between pictures 4.

Signed-off-by: Zhong Cong <congx.zhong@intel.com>

Conflicts:
	decoder/vaapidecoder_h264.cpp
h264dec: support gaps between pictures 5.

Signed-off-by: Zhong Cong <congx.zhong@intel.com>
h264dec: support gaps between pictures 6.

Signed-off-by: Zhong Cong <congx.zhong@intel.com>