misc: ipaddr.h: take const char pointers, add ipaddr_parse_ipv4_prefix_bin() to be consistent
misc: ipaddr.h: take const char pointers, add ipaddr_parse_ipv4_prefix_bin() to be consistent

Ernillew/badvpn,Ernillew/badvpn,Ernillew/badvpn,Ernillew/badvpn,Ernillew/badvpn