Fix saving/restoring window position for maximized windows

Save both the normal window geometry and its maximized position instead
of saving just its current position. This fixes restoring geometry of
the maximized windows as previously they were always restored on the
primary monitor, as their original position was lost.

Use the native {Get,Set}WindowPlacement() functions for a MSW-specific
wxTLWGeometry implementation to achieve this.

Closes #16335.

docs/changes.txt

@@ -88,6 +88,7 @@ wxMSW:
 
 - Fix hang after clearing wxTAB_TRAVERSAL style on a window with children.
 - Fix handling of AUX2 mouse button events (Trylz).
+- Fix saving/restoring window position for maximized windows.
 
 
 3.1.1: (released 2018-02-19)