patch 8.1.1880: cannot show extra info for completion in a popup window

Problem:    Cannot show extra info for completion in a popup window.
Solution:   Add the "popup" entry in 'completeopt'.
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 5557f63..79e0d0b 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 8.1.  Last change: 2019 Jul 31
+*options.txt*	For Vim version 8.1.  Last change: 2019 Aug 17
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1915,6 +1915,11 @@
 		    completion in the preview window.  Only works in
 		    combination with "menu" or "menuone".
 
+	   popup    Show extra information about the currently selected
+		    completion in a popup window.  Only works in combination
+		    with "menu" or "menuone".  Overrides "preview".
+		    {only works when compiled with the +textprop feature}
+
 	   noinsert Do not insert any text for a match until the user selects
 		    a match from the menu. Only works in combination with
 		    "menu" or "menuone". No effect if "longest" is present.
@@ -5650,6 +5655,8 @@
 			|+textprop| or |+quickfix| feature}
 	When not empty a popup window is used for commands that would open a
 	preview window.  See |preview-popup|.
+	Not used for the insert completion info, add "popup" to
+	'completeopt' for that.
 
 					*'previewwindow'* *'nopreviewwindow'*
 					*'pvw'* *'nopvw'* *E590*