package/freeswitch: add opencv3 optional dependency

opencv3 is an optional dependency since version 1.8.1 and
https://github.com/signalwire/freeswitch/commit/6483ab8b65886465863584e8dcfee57084030b9c

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
3 files changed