patch 8.1.1015: quickfix buffer shows up in list, can't get buffer number

Problem:    Quickfix buffer shows up in list, can't get buffer number.
Solution:   Make the quickfix buffer unlisted when the quickfix window is
            closed.  get the quickfix buffer number with getqflist().
            (Yegappan Lakshmanan, closes #4113)
diff --git a/runtime/doc/quickfix.txt b/runtime/doc/quickfix.txt
index 5589df9..0ceb231 100644
--- a/runtime/doc/quickfix.txt
+++ b/runtime/doc/quickfix.txt
@@ -496,6 +496,7 @@
 			second quickfix window.  If [height] is given the
 			existing window will be resized to it.
 
+							*quickfix-buffer*
 			The window will contain a special buffer, with
 			'buftype' equal to "quickfix".  Don't change this!
 			The window will have the w:quickfix_title variable set
@@ -504,7 +505,11 @@
 			status line if the value of 'statusline' is adjusted
 			properly. Whenever this buffer is modified by a
 			quickfix command or function, the |b:changedtick|
-			variable is incremented.
+			variable is incremented.  You can get the number of
+			this buffer using the getqflist() and getloclist()
+			functions by passing the 'qfbufnr' item. For a
+			location list, this buffer is wiped out when the
+			location list is removed.
 
 							*:lop* *:lopen*
 :lop[en] [height]	Open a window to show the location list for the
@@ -670,12 +675,18 @@
     " get the quickfix list window id
     :echo getqflist({'winid' : 0}).winid
 
+    " get the quickfix list window buffer number
+    :echo getqflist({'qfbufnr' : 0}).qfbufnr
+
     " get the context of the current location list
     :echo getloclist(0, {'context' : 0}).context
 
     " get the location list window id of the third window
     :echo getloclist(3, {'winid' : 0}).winid
 
+    " get the location list window buffer number of the third window
+    :echo getloclist(3, {'qfbufnr' : 0}).qfbufnr
+
     " get the file window id of a location list window (winnr: 4)
     :echo getloclist(4, {'filewinid' : 0}).filewinid
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