Repair commit e0c3fe9 to fix #521 which destroyed DnD from Wayland

It turns out it's necessary to memorize 2 event serial numbers :
- serial changed at each pointer and key event;
- pointer_enter_serial changed when pointer enters a surface
because this one and not any other is needed for exact cursor changes
by wl_pointer_set_cursor() in do_set_cursor().

1 files changed, 1 insertions, 0 deletions

diff --git a/src/drivers/Wayland/Fl_Wayland_Screen_Driver.H b/src/drivers/Wayland/Fl_Wayland_Screen_Driver.H
index e55531509..f08f9cd86 100644
--- a/src/drivers/Wayland/Fl_Wayland_Screen_Driver.H
+++ b/src/drivers/Wayland/Fl_Wayland_Screen_Driver.H
@@ -42,6 +42,7 @@ struct seat {
   struct wl_surface *pointer_focus;
   int pointer_scale;
   uint32_t serial;
+  uint32_t pointer_enter_serial;
   struct wl_data_device_manager *data_device_manager;
   struct wl_data_device *data_device;
   struct wl_data_source *data_source;