QMP: Introduce RESUME event

It's emitted when the Virtual Machine resumes execution.

We currently have the STOP event but don't have the matching
RESUME one, this means that clients are notified when the VM
is stopped but don't get anything when it resumes.

Let's fix that as it's already causing some trouble to libvirt.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/vl.c b/vl.c
index 9caf96d..999aac8 100644
--- a/vl.c
+++ b/vl.c
@@ -1689,6 +1689,7 @@
         vm_running = 1;
         vm_state_notify(1, 0);
         resume_all_vcpus();
+        monitor_protocol_event(QEVENT_RESUME, NULL);
     }
 }