[inactivity] Refactor inactivity module. Contributes to JB#31927

Use common prefix for all functions in inactivity module and shuffle
code so that functions that are related are close to each other.

Install datapipe trackers for related state variables instead of
polling them here and there.

Split implementation of "activity callback" feature in three layers:
object memory management, list of objects management and dbus
method call handlers.

Instead of defaulting to "active" state on mce startup, make it so
that initial state depends on what display state mce lands on. Also
make sure that a) on mce startup the initial state is always broadcast
b) the same state is not broadcast repeatedly.

Simplify code by omitting return value tracking in callback functions
where the return value is not actually used for anything meaningful.

Makefile

@@ -555,6 +555,7 @@ NORMALIZE_USES_SPC =\
 	modules/doubletap.h\
 	modules/filter-brightness-simple.h\
 	modules/keypad.h\
+	modules/inactivity.c\
 	modules/memnotify.c\
 	modules/memnotify.h\
 	modules/packagekit.c\
@@ -606,7 +607,6 @@ NORMALIZE_USES_TAB =\
 	modules/filter-brightness-als.c\
 	modules/filter-brightness-als.h\
 	modules/filter-brightness-simple.c\
-	modules/inactivity.c\
 	modules/keypad.c\
 	modules/led.c\
 	modules/led.h\

datapipe.c

@@ -842,7 +842,7 @@ void mce_datapipe_init(void)
 	setup_datapipe(&touchscreen_pipe, READ_ONLY, FREE_CACHE,
 		       sizeof (struct input_event), NULL);
 	setup_datapipe(&device_inactive_pipe, READ_WRITE, DONT_FREE_CACHE,
-		       0, GINT_TO_POINTER(FALSE));
+		       0, GINT_TO_POINTER(TRUE));
 	setup_datapipe(&lockkey_pipe, READ_ONLY, DONT_FREE_CACHE,
 		       0, GINT_TO_POINTER(0));
 	setup_datapipe(&keyboard_slide_pipe, READ_ONLY, DONT_FREE_CACHE,