add new -mon switch

Add -mon switch which maps pretty straight forward into the QemuOpts
internal representation:

  -mon chardev=<name>[,mode=[control|readline]][,[no]default]

Via config file:

[mon]
   chardev = "<name>"
   mode = "readline"
   default = "on"

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/vl.c b/vl.c
index bb9ffd3..d90975f 100644
--- a/vl.c
+++ b/vl.c
@@ -5284,6 +5284,14 @@
                 monitor_parse(optarg);
                 default_monitor = 0;
                 break;
+            case QEMU_OPTION_mon:
+                opts = qemu_opts_parse(&qemu_mon_opts, optarg, "chardev");
+                if (!opts) {
+                    fprintf(stderr, "parse error: %s\n", optarg);
+                    exit(1);
+                }
+                default_monitor = 0;
+                break;
             case QEMU_OPTION_chardev:
                 opts = qemu_opts_parse(&qemu_chardev_opts, optarg, "backend");
                 if (!opts) {