compositor: Keep track of what views were activated by clicking

Adds a weston_view_activate() that can be passed an additional active
flag WESTON_ACTIVATE_CLICKED, that the shell passes when a view was
activated by clicking.

This allows shell-independent components implement heuristics depending
on how a view was activated.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
diff --git a/libweston/compositor.c b/libweston/compositor.c
index 96eeb17..4a0bfef 100644
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -4685,6 +4685,8 @@
 	ec->output_id_pool = 0;
 	ec->repaint_msec = DEFAULT_REPAINT_WINDOW;
 
+	ec->activate_serial = 1;
+
 	if (!wl_global_create(ec->wl_display, &wl_compositor_interface, 4,
 			      ec, compositor_bind))
 		goto fail;