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/qemu-options.hx b/qemu-options.hx
index e05b2a0..7234447 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1589,6 +1589,13 @@
 non graphical mode.
 ETEXI
 
+DEF("mon", HAS_ARG, QEMU_OPTION_mon, \
+    "-mon chardev=[name][,mode=readline|control][,default]\n")
+STEXI
+@item -mon chardev=[name][,mode=readline|control][,default]
+Setup monitor on chardev @var{name}.
+ETEXI
+
 DEF("pidfile", HAS_ARG, QEMU_OPTION_pidfile, \
     "-pidfile file   write PID to 'file'\n")
 STEXI