v4l: Fixed memory leaks and inconsistent status return values 
v4l: Fixed memory leaks and inconsistent status return values 

by updating to c++ coding conventions

 - const correctness
 - use bool as return value
 - use explicit initialization instead of CLEAR macro/ memset
 - use cv namespace
opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv