libnetdissect code must include 'netdissect.h', not 'interface.h'

Moreover:
Remove netdissect.h include in interface.h
Move thiszone declaration in netdissect.h
Update a comment

1 files changed, 1 insertions, 1 deletions

diff --git a/in_cksum.c b/in_cksum.c
index caf4b6af..8ceaf104 100644
--- a/in_cksum.c
+++ b/in_cksum.c
@@ -41,7 +41,7 @@
 
 #include <netdissect-stdinc.h>
 
-#include "interface.h"
+#include "netdissect.h"
 
 /*
  * Checksum routine for Internet Protocol family headers (Portable Version).