Implement touch screen events on PGTK

* etc/NEWS: Better qualify entry for touch screen events.

* lisp/loadup.el (featurep 'pgtk): Load touch-screen.el.

* lisp/touch-screen.el: Revise list of systems where touch
screen events are reported.

* src/gtkutil.c (xg_create_frame_widgets): Request
GDK_TOUCH_MASK.

* src/pgtkfns.c (pgtk_frame_parm_handlers, tip_window): Pacify
compiler warning.

* src/pgtkterm.c (pgtk_free_frame_resources): Free touch points
linked to this frame.
(pgtk_link_touch_point, pgtk_unlink_touch_point)
(pgtk_unlink_touch_points, pgtk_find_touch_point): New
functions, ported from X.
(touch_event_cb): New event callback.
(pgtk_set_event_handler): Register `touch_event_cb' as handler
for `touch-event'.
(pgtk_delete_display): Free residual touch points on this
display.

* src/pgtkterm.h (struct pgtk_touch_point): New structure.
(struct pgtk_display_info) <touchpoints>: New field.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/pgtkfns.c b/src/pgtkfns.c
index 6a8efb6d0bf..bdc6c5836fa 100644
--- a/src/pgtkfns.c
+++ b/src/pgtkfns.c
@@ -945,6 +945,7 @@ unless TYPE is `png'.  */)
   return pgtk_cr_export_frames (frames, surface_type);
 }
 
+extern frame_parm_handler pgtk_frame_parm_handlers[];
 frame_parm_handler pgtk_frame_parm_handlers[] =
   {
     gui_set_autoraise,          /* generic OK */
@@ -2619,7 +2620,7 @@ static Lisp_Object tip_frame;
 
 /* The window-system window corresponding to the frame of the
    currently visible tooltip.  */
-GtkWidget *tip_window;
+static GtkWidget *tip_window;
 
 /* A timer that hides or deletes the currently visible tooltip when it
    fires.  */