WorkStruct: Separate delayable and non-delayable events.

Separate delayable work items from non-delayable work items be splitting them
into a separate structure (delayed_work), which incorporates a work_struct and
the timer_list removed from work_struct.

The work_struct struct is huge, and this limits it's usefulness.  On a 64-bit
architecture it's nearly 100 bytes in size.  This reduces that by half for the
non-delayable type of event.

Signed-Off-By: David Howells <dhowells@redhat.com>
diff --git a/include/linux/aio.h b/include/linux/aio.h
index 0d71c00..9e350fd4 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -194,7 +194,7 @@
 
 	struct aio_ring_info	ring_info;
 
-	struct work_struct	wq;
+	struct delayed_work	wq;
 };
 
 /* prototypes */