Changing the message union to anonymous.

This allows us to write things like this:
  message m;
  m.m_notify.interrupts = new_value;

or
  message *mp;
  mp->m_notify.interrupts = new_value;

The shorthands macro have been adapted for the new scheme, and will be
kept as long as we have generic messages being used.

Change-Id: Icfd02b5f126892b1d5d2cebe8c8fb02b180000f7

servers/pm/main.c

@@ -65,7 +65,7 @@ int main()
 	/* Check for system notifications first. Special cases. */
 	if (is_ipc_notify(ipc_status)) {
 		if (_ENDPOINT_P(m_in.m_source) == CLOCK)
-			expire_timers(m_in.NOTIFY_TIMESTAMP);
+			expire_timers(m_in.m_notify.timestamp);
 
 		/* done, continue */
 		continue;