Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/usr_25.txt b/runtime/doc/usr_25.txt
index c193d54..f5be3e0 100644
--- a/runtime/doc/usr_25.txt
+++ b/runtime/doc/usr_25.txt
@@ -1,4 +1,4 @@
-*usr_25.txt*	For Vim version 8.0.  Last change: 2016 Mar 28
+*usr_25.txt*	For Vim version 8.1.  Last change: 2016 Mar 28
 
 		     VIM USER MANUAL - by Bram Moolenaar