Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/sign.txt b/runtime/doc/sign.txt
index b61e4f1..dab63b1 100644
--- a/runtime/doc/sign.txt
+++ b/runtime/doc/sign.txt
@@ -1,4 +1,4 @@
-*sign.txt*      For Vim version 8.0.  Last change: 2016 Aug 17
+*sign.txt*      For Vim version 8.1.  Last change: 2016 Aug 17
 
 
 		  VIM REFERENCE MANUAL    by Gordon Prieur