Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/usr_31.txt b/runtime/doc/usr_31.txt
index 2344a98..13de489 100644
--- a/runtime/doc/usr_31.txt
+++ b/runtime/doc/usr_31.txt
@@ -1,4 +1,4 @@
-*usr_31.txt*	For Vim version 8.0.  Last change: 2007 May 08
+*usr_31.txt*	For Vim version 8.1.  Last change: 2007 May 08
 
 		     VIM USER MANUAL - by Bram Moolenaar