Defines starting with `n' in src/slirp

• NB_ADDR src/slirp/bootp.c:28
• NEED_TYPEDEFS src/slirp/slirp_config.h:78
• _NETINET_ICMP_VAR_H_ src/slirp/icmp_var.h:34
• _NETINET_IP_ICMP_H_ src/slirp/ip_icmp.h:34
• NO_UNIX_SOCKETS src/slirp/slirp_config.h:111
• NS_INADDRSZ src/slirp/misc.c:17
• NS_INT16SZ src/slirp/misc.c:18
• NULL src/slirp/slirp.h:253