patch 8.2.0933: 'quickfixtextfunc' does not get window ID of location list

Problem:    'quickfixtextfunc' does not get window ID of location list.
Solution:   Add "winid" to the dict argument. (Yegappan Lakshmanan,
            closes #6222)
diff --git a/runtime/doc/quickfix.txt b/runtime/doc/quickfix.txt
index 4f3112c..982044c 100644
--- a/runtime/doc/quickfix.txt
+++ b/runtime/doc/quickfix.txt
@@ -1953,6 +1953,9 @@
 
     quickfix	set to 1 when called for a quickfix list and 0 when called for
 		a location list.
+    winid	for a location list, set to the id of the window with the
+		location list. For a quickfix list, set to 0. Can be used in
+		getloclist() to get the location list entry.
     id		quickfix or location list identifier
     idx		index of the entry in the quickfix or location list