[cleanup] convert bzero() deprecated by POSIX to memset()

autoscan 2.62 complains about bzero(), so a good fix
nowadays is to just replace it.
diff --git a/isisd/isis_lsp.c b/isisd/isis_lsp.c
index 48e3147..50289db 100644
--- a/isisd/isis_lsp.c
+++ b/isisd/isis_lsp.c
@@ -769,7 +769,7 @@
   /* for the hostname tlv */
   if (lsp->tlv_data.hostname)
     {
-      bzero (hostname, sizeof (hostname));
+      memset (hostname, 0, sizeof (hostname));
       memcpy (hostname, lsp->tlv_data.hostname->name,
 	      lsp->tlv_data.hostname->namelen);
       vty_out (vty, "  Hostname: %s%s", hostname, VTY_NEWLINE);
diff --git a/zebra/irdp_interface.c b/zebra/irdp_interface.c
index b3a838b..d982c23 100644
--- a/zebra/irdp_interface.c
+++ b/zebra/irdp_interface.c
@@ -101,7 +101,7 @@
 
   zi = ifp->info;
 
-  bzero (&m, sizeof (m));
+  memset (&m, 0, sizeof (m));
   m.imr_multiaddr.s_addr = htonl (group);
   p = irdp_get_prefix(ifp);
 
diff --git a/zebra/irdp_packet.c b/zebra/irdp_packet.c
index 3c5f155..6003837 100644
--- a/zebra/irdp_packet.c
+++ b/zebra/irdp_packet.c
@@ -332,7 +332,7 @@
 	zlog_warn("sendto %s", safe_strerror (errno));
   }
 
-  bzero(&sockdst,sizeof(sockdst));
+  memset(&sockdst,0,sizeof(sockdst));
   sockdst.sin_family=AF_INET;
   sockdst.sin_addr.s_addr = dst;