opencv: add hidden symbol BR2_PACKAGE_OPENCV_USE_DEPRECATED_CV_H

This new hidden symbol aims to automatically select all OpenCV modules
required when another package use the deprecated OpenCV 'cv.h' headers.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
vlc: rework opencv support

Use the newly introduced BR2_PACKAGE_OPENCV_USE_DEPRECATED_CV_H symbol
to handle all opencv module dependencies.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
gst1-plugins-bad: rework opencv plugin dependencies

Use the newly introduced BR2_PACKAGE_OPENCV_USE_DEPRECATED_CV_H to
select all required OPenCV module dependencies.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>