Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/pi_spec.txt b/runtime/doc/pi_spec.txt
index 7921371..abe5f11 100644
--- a/runtime/doc/pi_spec.txt
+++ b/runtime/doc/pi_spec.txt
@@ -1,4 +1,4 @@
-*pi_spec.txt*   For Vim version 8.0.  Last change: 2006 Apr 24
+*pi_spec.txt*   For Vim version 8.1.  Last change: 2006 Apr 24
 
 by Gustavo Niemeyer ~