Replace uses of sprintf(3) with snprintf(3).

At -00, the compiler warns about sprintf(3), and it is promoted to an
error by -Werror.

Change-Id: Ibb380d27d7eb09dda8ac785be2478d656b379190
diff --git a/libc/dns/resolv/res_query.c b/libc/dns/resolv/res_query.c
index 6cd9b15..09be8b4 100644
--- a/libc/dns/resolv/res_query.c
+++ b/libc/dns/resolv/res_query.c
@@ -414,7 +414,7 @@
 			RES_SET_H_ERRNO(statp, NO_RECOVERY);
 			return (-1);
 		}
-		sprintf(nbuf, "%s.%s", name, domain);
+		snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
 	}
 	return (res_nquery(statp, longname, class, type, answer, anslen));
 }