Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/vi_diff.txt b/runtime/doc/vi_diff.txt
index 9a4981f..a395c88 100644
--- a/runtime/doc/vi_diff.txt
+++ b/runtime/doc/vi_diff.txt
@@ -1,4 +1,4 @@
-*vi_diff.txt*   For Vim version 8.0.  Last change: 2016 Aug 16
+*vi_diff.txt*   For Vim version 8.1.  Last change: 2016 Aug 16
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar