When searching for uninitialized memory usage add ensure that the entire

struct is set to zero.

PR:		bin/166483
Submitted by:	Roy Marples <roy@marples.name>
Reviewed by:	delphij
Approved by:	cperciva
MFC after:	3 days

lib/libc/net/if_nametoindex.c

@@ -70,6 +70,9 @@ if_nametoindex(const char *ifname)
 
 	s = _socket(AF_INET, SOCK_DGRAM, 0);
 	if (s != -1) {
+#ifdef PURIFY
+		memset(&ifr, 0, sizeof(ifr));
+#endif
 		strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
 		if (_ioctl(s, SIOCGIFINDEX, &ifr) != -1) {
 			_close(s);