w32_common: prevent MOUSE_BTN0 sticking after drag

The window doesn't recieve a WM_LBUTTONUP message after it's dragged,
probably because it's swallowed by the modal loop. To stop the button
from sticking, release it manually when the drag is complete.

video/out/w32_common.c

@@ -330,6 +330,8 @@ static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam,
                 // Window dragging hack
                 ReleaseCapture();
                 SendMessage(hWnd, WM_NCLBUTTONDOWN, HTCAPTION, 0);
+                mp_input_put_key(vo->input_ctx, MP_MOUSE_BTN0 |
+                                                MP_KEY_STATE_UP);
                 return 0;
             }
         }