Revert "mi: unexport miMarkWindow()"

This reverts commit bcbb6eec62.

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2102>

mi/mi.h

@@ -286,6 +286,9 @@ extern _X_EXPORT void miPolylines(DrawablePtr pDrawable,
 
 /* miwindow.c */
 
+extern _X_EXPORT void miMarkWindow(WindowPtr    /*pWin */
+    );
+
 extern _X_EXPORT Bool miMarkOverlappedWindows(WindowPtr /*pWin */ ,
                                               WindowPtr /*pFirst */ ,
                                               WindowPtr *       /*ppLayerWin */

mi/mi_priv.h

@@ -54,6 +54,5 @@ int miValidateTree(WindowPtr pParent, WindowPtr pChild, VTKind kind);
 
 void miClearToBackground(WindowPtr pWin, int x, int y, int w, int h,
                          Bool generateExposures);
-void miMarkWindow(WindowPtr pWin);
 
 #endif /* _XSERVER_MI_PRIV_H */

mi/mioverlay.c

@@ -3,13 +3,11 @@
 
 #include <X11/X.h>
 
-#include "mi/mi_priv.h"
-
-
 #include "scrnintstr.h"
 #include <X11/extensions/shapeproto.h>
 #include "validate.h"
 #include "windowstr.h"
+#include "mi.h"
 #include "gcstruct.h"
 #include "regionstr.h"
 #include "privates.h"