input: use doubles in the interfaces to notify of input events

This patch is a further step in the wl_fixed_t internal sanitization.
It changes the notify_* functions to take doubles instead of wl_fixed_t
but does not change how these are stored in the various input structs
yet, except for weston_pointer_axis_event.
However this already allows to remove all wl_fixed_t usage in places
like the libinput or the x11 backend.

Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index e1fefae..24437d8 100644
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -4786,7 +4786,7 @@
 	if (!shsurf)
 		return;
 
-	shsurf->view->alpha -= wl_fixed_to_double(event->value) * step;
+	shsurf->view->alpha -= event->value * step;
 
 	if (shsurf->view->alpha > 1.0)
 		shsurf->view->alpha = 1.0;
@@ -4799,7 +4799,7 @@
 
 static void
 do_zoom(struct weston_seat *seat, uint32_t time, uint32_t key, uint32_t axis,
-	wl_fixed_t value)
+	double value)
 {
 	struct weston_compositor *compositor = seat->compositor;
 	struct weston_pointer *pointer = weston_seat_get_pointer(seat);
@@ -4823,7 +4823,7 @@
 			else if (axis == WL_POINTER_AXIS_VERTICAL_SCROLL)
 				/* For every pixel zoom 20th of a step */
 				increment = output->zoom.increment *
-					    -wl_fixed_to_double(value) / 20.0;
+					    -value / 20.0;
 			else
 				increment = 0;