[MEDIUM] indicate a reason for a task wakeup

It's very frequent to require some information about the
reason why a task is running. Some flags have been added
so that a task now knows if it got woken up due to I/O
completion, timeout, etc...
diff --git a/src/stream_sock.c b/src/stream_sock.c
index 459da71..52860ea 100644
--- a/src/stream_sock.c
+++ b/src/stream_sock.c
@@ -239,7 +239,7 @@
 	if (!(b->flags & BF_READ_ACTIVITY))
 		goto out_skip_wakeup;
  out_wakeup:
-	task_wakeup(fdtab[fd].owner);
+	task_wakeup(fdtab[fd].owner, TASK_WOKEN_IO);
 
  out_skip_wakeup:
 	fdtab[fd].ev &= ~FD_POLL_IN;
@@ -411,7 +411,7 @@
 	if (!(b->flags & BF_WRITE_ACTIVITY))
 		goto out_skip_wakeup;
  out_wakeup:
-	task_wakeup(fdtab[fd].owner);
+	task_wakeup(fdtab[fd].owner, TASK_WOKEN_IO);
 
  out_skip_wakeup:
 	fdtab[fd].ev &= ~FD_POLL_OUT;