Simplify cursor window logic

src/win32_platform.h

@@ -254,6 +254,8 @@ typedef struct _GLFWlibraryWin32
     short int           nativeKeys[GLFW_KEY_LAST + 1];
     // Where to place the cursor when re-enabled
     double              restoreCursorPosX, restoreCursorPosY;
+    // The window whose disabled cursor mode is active
+    _GLFWwindow*        disabledCursorWindow;
 
     struct {
         HINSTANCE       instance;