Initialize the __res_state structure used for dns purposes

to all 0's prior to using it. This is due to valgrind's complaints
on issue #12284 as well as an excerpt found in "Description" portion
of the online man page found here:

http://www.iti.cs.tu-bs.de/cgi-bin/UNIXhelp/man-cgi?res_nquery+3RESOLV

(pertains to issue #12284 but does not necessarily close it)



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@112138 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/dns.c

@@ -255,6 +255,7 @@ int ast_search_dns(void *context,
 	int res, ret = -1;
 
 #ifdef HAVE_RES_NINIT
+	memset(&dnsstate, 0, sizeof(dnsstate));
 	res_ninit(&dnsstate);
 	res = res_nsearch(&dnsstate, dname, class, type, answer, sizeof(answer));
 #else