OpenCV 3.2 and libv4l 1.12 on RPi3

libv4l source from http://git.,inuxtv.org/v4l-utils.git does not work well on RPi3.  OpenCV3.2 build will experience error.

Instead, we should get Debian v4l-utils-1.12.5 source package.  OpenCV3.2 will build successively.

One minor item is that after install v4l, the following line shall be added.

sudo ln -s /usr/local/include/libv4l1-videodev.h /usr/include/linux/videodev.h