Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/README.txt b/README.txt
index eefa2ef..e0132dc 100644
--- a/README.txt
+++ b/README.txt
@@ -1,4 +1,4 @@
-README.txt for version 8.0 of Vim: Vi IMproved.
+README.txt for version 8.1 of Vim: Vi IMproved.
 
 
 WHAT IS VIM?