Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/if_pyth.txt b/runtime/doc/if_pyth.txt
index 50e93ba..89baef4 100644
--- a/runtime/doc/if_pyth.txt
+++ b/runtime/doc/if_pyth.txt
@@ -1,4 +1,4 @@
-*if_pyth.txt*   For Vim version 8.0.  Last change: 2018 Jan 30
+*if_pyth.txt*   For Vim version 8.1.  Last change: 2018 Jan 30
 
 
 		  VIM REFERENCE MANUAL    by Paul Moore