Fix wxEVT_TREE_STATE_IMAGE_CLICK generation in wxMSW wxTreeCtrl.

Use GET_{X,Y}_LPARAM() to extract them from the event position, which handle
negative coordinates (and coordinates can perfectly well be negative when
using multiple displays) correctly, unlike {LO,HI}WORD().

Closes #16812.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78420 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/treectrl.cpp

@@ -3612,8 +3612,8 @@ bool wxTreeCtrl::MSWOnNotify(int idCtrl, WXLPARAM lParam, WXLPARAM *result)
             {
                 DWORD pos = GetMessagePos();
                 POINT point;
-                point.x = LOWORD(pos);
-                point.y = HIWORD(pos);
+                point.x = GET_X_LPARAM(pos);
+                point.y = GET_Y_LPARAM(pos);
                 ::MapWindowPoints(HWND_DESKTOP, GetHwnd(), &point, 1);
                 int htFlags = 0;
                 wxTreeItemId item = HitTest(wxPoint(point.x, point.y), htFlags);