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

drivers/filter/driver.c

@@ -583,7 +583,7 @@ static int flt_receive(message *mess, int which)
 		}
 
 		if(mess->m_source == CLOCK && is_ipc_notify(ipc_status)) {
-			if (mess->NOTIFY_TIMESTAMP < flt_alarm((clock_t) -1)) {
+			if (mess->m_notify.timestamp < flt_alarm((clock_t) -1)) {
 #if DEBUG
 				printf("Filter: SKIPPING old alarm "
 					"notification\n");