Update runtime files
diff --git a/runtime/doc/index.txt b/runtime/doc/index.txt
index d1c3c87..f20c706 100644
--- a/runtime/doc/index.txt
+++ b/runtime/doc/index.txt
@@ -1,4 +1,4 @@
-*index.txt* For Vim version 8.1. Last change: 2019 Jun 09
+*index.txt* For Vim version 8.1. Last change: 2019 Jun 16
VIM REFERENCE MANUAL by Bram Moolenaar
@@ -1241,6 +1241,7 @@
|:compiler| :comp[iler] do settings for a specific compiler
|:continue| :con[tinue] go back to :while
|:confirm| :conf[irm] prompt user when confirmation required
+|:const| :cons[t] create a variable as a constant
|:copen| :cope[n] open quickfix window
|:cprevious| :cp[revious] go to previous error
|:cpfile| :cpf[ile] go to last error in previous file