yubikey.h requires char *, cast to silence warning
yubikey.h requires char *, cast to silence warning

yubikey.h from yubico-c defines yubikey_hex_*() to have a char * as first
parameter, where we use unisgned char[] here. Add a cast to silence the
warning this generates.

eworm-de/yubikey-personalization,dmitriykuptsov/yubikey-personalization,dmitriykuptsov/yubikey-personalization,Yubico/yubikey-personalization-dpkg,Yubico/yubikey-personalization,dmitriykuptsov/yubikey-personalization,Yubico/yubikey-personalization,Yubico/yubikey-personalization-dpkg,eworm-de/yubikey-personalization,Yubico/yubikey-personalization-dpkg,eworm-de/yubikey-personalization