Add vaapi into namespace.

Signed-off-by: Tang Xin <xin.t.tang@intel.com>
Add Capi wrapper controlled by enable-capi.

Signed-off-by: Tang Xin <xin.t.tang@intel.com>
encode: release derived image of input surface after data uploading

driver does strict check on buffer owership upon vaBeginPicture() now.