Merge isisd into the Quagga's framework:
  - add privs support
  - use misc quagga's definitions
  - make it compile"able"
  - fix segfault cases related to hostname()
  - add debug isis xxx command

This patch has been approved by Paul Jakma.
diff --git a/lib/vty.c b/lib/vty.c
index 6063290..2b823e0 100644
--- a/lib/vty.c
+++ b/lib/vty.c
@@ -626,6 +626,7 @@
     case RMAP_NODE:
     case OSPF_NODE:
     case OSPF6_NODE:
+    case ISIS_NODE:
     case KEYCHAIN_NODE:
     case KEYCHAIN_KEY_NODE:
     case MASC_NODE:
@@ -1030,6 +1031,7 @@
     case RMAP_NODE:
     case OSPF_NODE:
     case OSPF6_NODE:
+    case ISIS_NODE:
     case KEYCHAIN_NODE:
     case KEYCHAIN_KEY_NODE:
     case MASC_NODE: