Revert "dix: drop superfluous XineramaGetCursorScreen()"

This reverts commit 6c7c4fdc7e.

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2058>

include/cursor.h

@@ -57,6 +57,8 @@ SOFTWARE.
 /* Provide support for alpha composited cursors */
 #define ARGB_CURSOR
 
+struct _DeviceIntRec;
+
 typedef struct _Cursor *CursorPtr;
 // FUN FACT: If you typedef a pointer type, like the `CursorPtr` above
 // then `const CursorPtr` or `CursorPtr const` actually means `struct _Cursor *const`, a constant pointer
@@ -68,4 +70,8 @@ typedef struct _CursorMetric *CursorMetricPtr;
 extern _X_EXPORT int FreeCursor(void *pCurs,
                                 XID cid);
 
+#ifdef PANORAMIX
+extern _X_EXPORT int XineramaGetCursorScreen(struct _DeviceIntRec *pDev);
+#endif                          /* PANORAMIX */
+
 #endif                          /* CURSOR_H */