Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/howto.txt b/runtime/doc/howto.txt
index a1b2578..f697310 100644
--- a/runtime/doc/howto.txt
+++ b/runtime/doc/howto.txt
@@ -1,4 +1,4 @@
-*howto.txt*	For Vim version 8.0.  Last change: 2006 Apr 02
+*howto.txt*	For Vim version 8.1.  Last change: 2006 Apr 02
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar