patch 9.0.0913: only change in current window triggers the WinScrolled event

Problem:    Only a change in the current window triggers the WinScrolled
            event.
Solution:   Trigger WinScrolled if any window scrolled or changed size.
            (issue #11576)
diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index 5051cc3..86ae60f 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -1372,16 +1372,32 @@
 
 							*WinScrolled*
 WinScrolled			After scrolling the content of a window or
-				resizing a window.
-				The pattern is matched against the
-				|window-ID|.  Both <amatch> and <afile> are
-				set to the |window-ID|.
-				Non-recursive (the event cannot trigger
-				itself).  However, if the command causes the
-				window to scroll or change size another
+				resizing a window in the current tab page.
+
+				When more than one window scrolled or resized
+				only one WinScrolled event is triggered.  You
+				can use the `winlayout()` and `getwininfo()`
+				functions to see what changed.
+
+				The pattern is matched against the |window-ID|
+				of the first window that scrolled or resized.
+				Both <amatch> and <afile> are set to the
+				|window-ID|.
+
+				Only starts triggering after startup finished
+				and the first screen redraw was done.
+
+				Non-recursive: the event will not trigger
+				while executing commands for the WinScrolled
+				event.  However, if the command causes a
+				window to scroll or change size, then another
 				WinScrolled event will be triggered later.
+
 				Does not trigger when the command is added,
 				only after the first scroll or resize.
+							*E1312*
+				It is not allowed to change the window layout
+				here (split, close or move windows).
 
 ==============================================================================
 6. Patterns					*autocmd-patterns* *{aupat}*