package/libv4l: add optional support for libgl
libv4l has optional support for OpenGL:
https://git.linuxtv.org/v4l-utils.git/tree/configure.ac#n160
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>