Use non-static reentrancy guard in wxScrollHelper::AdjustScrollbars().

This prevented calls to AdjustScrollbars() of another window from doing
anything if they were called due to a size change from AdjustScrollbars() of
an outer window.

Closes #16852.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78483 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/scrolwin.h

@@ -10,6 +10,8 @@
 #ifndef _WX_GENERIC_SCROLLWIN_H_
 #define _WX_GENERIC_SCROLLWIN_H_
 
+#include "wx/recguard.h"
+
 // ----------------------------------------------------------------------------
 // generic wxScrollHelper implementation
 // ----------------------------------------------------------------------------
@@ -45,6 +47,7 @@ private:
 
     wxScrollbarVisibility m_xVisibility,
                           m_yVisibility;
+    wxRecursionGuardFlag m_adjustScrollFlagReentrancy;
 
     wxDECLARE_NO_COPY_CLASS(wxScrollHelper);
 };