Fix useless fields in interface.h.

interface.h

@@ -86,11 +86,9 @@ struct interface {
     char have_buffered_id;
     char have_buffered_nh;
     char have_buffered_prefix;
-    char have_buffered_src_prefix;
     unsigned char buffered_id[16];
     unsigned char buffered_nh[4];
     unsigned char buffered_prefix[16];
-    unsigned char buffered_src_prefix[16];
     unsigned char *sendbuf;
     struct buffered_update *buffered_updates;
     int num_buffered_updates;

message.c

@@ -813,7 +813,6 @@ flushbuf(struct interface *ifp)
     ifp->have_buffered_id = 0;
     ifp->have_buffered_nh = 0;
     ifp->have_buffered_prefix = 0;
-    ifp->have_buffered_src_prefix = 0;
     ifp->flush_timeout.tv_sec = 0;
     ifp->flush_timeout.tv_usec = 0;
 }