package/vlc: add opencv support

This change adds 2 patches (backported from upstream) to vlc fixing the
build against opencv2 APIs.
This allows to select the minimal set of opencv modules when opencv
support is enabled.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>