Vim 8.1 release

Update version number and information.  Fix a couple of tests.
diff --git a/runtime/doc/if_perl.txt b/runtime/doc/if_perl.txt
index 11b1440..a06954e 100644
--- a/runtime/doc/if_perl.txt
+++ b/runtime/doc/if_perl.txt
@@ -1,4 +1,4 @@
-*if_perl.txt*   For Vim version 8.0.  Last change: 2017 Nov 24
+*if_perl.txt*   For Vim version 8.1.  Last change: 2017 Nov 24
 
 
 		  VIM REFERENCE MANUAL    by Sven Verdoolaege