Made wxBORDER_THEME the same as wxBORDER_DEFAULT

Moved wxControl::GetBorderStyle into wxWindowMSW::GetBorderStyle
but added GetBorderStyle to have the same behaviour as before (so e.g.
notebook panels don't get borders)
Improved help window borders


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@47963 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/window.h

@@ -438,6 +438,9 @@ public:
     // wxControl
     virtual wxBorder GetDefaultBorderForControl() const;
 
+    // choose the default border for this window
+    virtual wxBorder GetDefaultBorder() const;
+
     // synthesize a wxEVT_LEAVE_WINDOW event and set m_mouseInWindow to false
     void GenerateMouseLeave();