nhrpd: implement next hop resolution protocol

This provides DMVPN support and integrates to strongSwan. Please read
README.nhrpd and README.kernel for more details.
diff --git a/lib/log.c b/lib/log.c
index 42b7717..d437066 100644
--- a/lib/log.c
+++ b/lib/log.c
@@ -53,6 +53,7 @@
   "ISIS",
   "PIM",
   "MASC",
+  "NHRP",
   NULL,
 };
 
@@ -986,6 +987,8 @@
 	return ZEBRA_ROUTE_BGP;
       else if (strncmp (s, "ba", 2) == 0)
 	return ZEBRA_ROUTE_BABEL;
+      else if (strncmp (s, "n", 1) == 0)
+	return ZEBRA_ROUTE_NHRP;
     }
   if (afi == AFI_IP6)
     {
@@ -1005,6 +1008,8 @@
 	return ZEBRA_ROUTE_BGP;
       else if (strncmp (s, "ba", 2) == 0)
 	return ZEBRA_ROUTE_BABEL;
+      else if (strncmp (s, "n", 1) == 0)
+	return ZEBRA_ROUTE_NHRP;
     }
   return -1;
 }