Add help button support to wxRibbonBar.

Optionally show standard "Help" question mark button in the ribbon top right
corner and generate the appropriate event for it.

Closes #14576.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72495 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/ribbon/panel.h

@@ -84,6 +84,8 @@ public:
 
     long GetFlags() { return m_flags; }
 
+    void HideIfExpanded();
+
 protected:
     virtual wxSize DoGetBestSize() const;
     virtual wxSize GetPanelSizerBestSize() const;