Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/pi_tar.txt b/runtime/doc/pi_tar.txt
index 1b03d31..7a6faf1 100644
--- a/runtime/doc/pi_tar.txt
+++ b/runtime/doc/pi_tar.txt
@@ -1,4 +1,4 @@
-*pi_tar.txt*	For Vim version 8.0.  Last change: 2013 Apr 17
+*pi_tar.txt*	For Vim version 8.1.  Last change: 2013 Apr 17
 
 		       +====================+
 		       | Tar File Interface |