patch 8.1.2192: cannot easily fill the info popup asynchronously

Problem:    Cannot easily fill the info popup asynchronously.
Solution:   Add the "popuphidden" value to 'completeopt'. (closes #4924)
diff --git a/runtime/doc/insert.txt b/runtime/doc/insert.txt
index dfc3541..d28bf59 100644
--- a/runtime/doc/insert.txt
+++ b/runtime/doc/insert.txt
@@ -1,4 +1,4 @@
-*insert.txt*    For Vim version 8.1.  Last change: 2019 Sep 27
+*insert.txt*    For Vim version 8.1.  Last change: 2019 Oct 20
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -1138,6 +1138,27 @@
 After the info popup is created it can be found with |popup_findinfo()| and
 properties can be changed with |popup_setoptions()|.
 
+						*complete-popuphidden*
+If the information for the popup is obtained asynchronously, use "popuphidden"
+in 'completeopt'.  The info popup will then be initally hidden and
+|popup_show()| must be called once it has been filled with the info.  This can
+be done with a |CompleteChanged| autocommand, something like this: >
+	set completeopt+=popuphidden
+	au CompleteChanged * call UpdateCompleteInfo()
+	func UpdateCompleteInfo()
+	  " Cancel any pending info fetch
+	  let item = v:event.completed_item
+	  " Start fetching info for the item then call ShowCompleteInfo(info)
+	endfunc
+	func ShowCompleteInfo(info)
+	  let id = popup_findinfo()
+	  if id
+	    call popup_settext(id, 'async info: ' .. a:info)
+	    call popup_show(id)
+	  endif
+	endfunc
+
+<						*complete-item-kind*
 The "kind" item uses a single letter to indicate the kind of completion.  This
 may be used to show the completion differently (different color or icon).
 Currently these types can be used:
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 8436c8a..e62ee89 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 Sep 28
+*options.txt*	For Vim version 8.1.  Last change: 2019 Oct 20
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1919,6 +1919,13 @@
 		    See |'completepopup'| for specifying properties.
 		    {only works when compiled with the |+textprop| feature}
 
+	   popuphidden
+	   	    Just like "popup" but initially hide the popup.  Use a
+		    |CompleteChanged| autocommand to fetch the info and call
+		    |popup_show()| once the popup has been filled.
+		    See the example at |complete-popuphidden|.
+		    {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.