Steal the window back when the WM reparents it

I've seen this happen once or twice. Earlier on (in #40) we could get
away with just reparenting the window another time. But here both
reparents succeed, and the issue still happens. But a reparent notify
for `parent_window` did appear on system affected by this issue, which
is very odd. Hopefully this will help.

src/wine-host/editor.h

@@ -245,6 +245,11 @@ class Editor {
                              uint32_t data1,
                              uint32_t data2) const noexcept;
 
+    /**
+     * Reparent `wine_window` to `parent_window`. This includes the flush.
+     */
+    void do_reparent() const;
+
     /**
      * Start the XEmbed procedure when `use_xembed` is enabled. This should be
      * rerun whenever visibility changes.