package/zxing-cpp: add optional opencv dependency

Bumping to version e0e40dd in commit
ad9c5bbf included the following upstream
commit:
https://github.com/glassechidna/zxing-cpp/commit/bccad40551573d150fbe8e295636e6277dcf6889



This commit adds an optional dependency on opencv so add it and fix it
through two patches

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>