Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/helphelp.txt b/runtime/doc/helphelp.txt
index 80fc70c..29941c1 100644
--- a/runtime/doc/helphelp.txt
+++ b/runtime/doc/helphelp.txt
@@ -1,4 +1,4 @@
-*helphelp.txt*	For Vim version 8.0.  Last change: 2017 Mar 19
+*helphelp.txt*	For Vim version 8.1.  Last change: 2017 Mar 19
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar