Fix go-mode.el to work on empty buffers

Fixes #8.

R=agl, agl1, rsc
https://golang.org/cl/153056

misc/emacs/go-mode.el

@@ -436,7 +436,7 @@ functions, and some types.  It also provides indentation that is
   ;; Remove stale text properties
   (save-restriction
     (widen)
-    (remove-list-of-text-properties 1 (buffer-size)
+    (remove-list-of-text-properties 1 (+ (buffer-size) 1)
                                     '(go-mode-cs go-mode-nesting)))
 
   ;; Reset the syntax mark caches