sdl: improve grab exiting instructions

It might not be obvious what "grab" is.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/sdl.c b/sdl.c
index f26035c..1d1e100 100644
--- a/sdl.c
+++ b/sdl.c
@@ -415,11 +415,11 @@
         status = " [Stopped]";
     else if (gui_grab) {
         if (alt_grab)
-            status = " - Press Ctrl-Alt-Shift to exit grab";
+            status = " - Press Ctrl-Alt-Shift to exit mouse grab";
         else if (ctrl_grab)
-            status = " - Press Right-Ctrl to exit grab";
+            status = " - Press Right-Ctrl to exit mouse grab";
         else
-            status = " - Press Ctrl-Alt to exit grab";
+            status = " - Press Ctrl-Alt to exit mouse grab";
     }
 
     if (qemu_name) {