Add a pc-0.11 machine type and make the pc type an alias

The pc-0.11 type allows users of qemu-0.11 to use a machine type which
they know will remain compatible when the upgrade to qemu-0.12.

Management tools may choose to canonicalize the 'pc' machine type to
'pc-0.11' so that if the 'pc' alias changes target in future versions
of qemu, the machine type used will remain compatible.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/pc.c

@@ -1512,7 +1512,8 @@ void cmos_set_s3_resume(void)
 }
 
 static QEMUMachine pc_machine = {
-    .name = "pc",
+    .name = "pc-0.11",
+    .alias = "pc",
     .desc = "Standard PC",
     .init = pc_init_pci,
     .max_cpus = 255,