timer: introduce new QEMU_CLOCK_VIRTUAL_RT clock

This patch introduces new QEMU_CLOCK_VIRTUAL_RT clock, which
should be used for icount warping.  In the next patch, it
will be used to avoid a huge icount warp when a virtual
machine is stopped for a long time.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/qemu-timer.c b/qemu-timer.c
index 00a5d35..f4b4b6a 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -566,6 +566,8 @@
             notifier_list_notify(&clock->reset_notifiers, &now);
         }
         return now;
+    case QEMU_CLOCK_VIRTUAL_RT:
+        return cpu_get_clock();
     }
 }