Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/os_msdos.txt b/runtime/doc/os_msdos.txt
index 6206ac8..50fb4e8 100644
--- a/runtime/doc/os_msdos.txt
+++ b/runtime/doc/os_msdos.txt
@@ -1,4 +1,4 @@
-*os_msdos.txt*  For Vim version 8.0.  Last change: 2016 Feb 26
+*os_msdos.txt*  For Vim version 8.1.  Last change: 2016 Feb 26
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar