qemu-char: Call fe_claim / fe_release when not using qdev chr properties

chardev-frontends need to explictly check, increase and decrement the
avail_connections "property" of the chardev when they are not using a
qdev-chardev-property for the chardev.

This fixes things like:
qemu-kvm -chardev stdio,id=foo -device isa-serial,chardev=foo \
  -mon chardev=foo

Working, where they should fail. Most of the changes here are due to
old hardware emulation code which is using serial_hds directly rather then
a qdev-chardev-property.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Message-id: 1364412581-3672-3-git-send-email-hdegoede@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

gdbstub.c

@@ -3025,6 +3025,7 @@ int gdbserver_start(const char *device)
         if (!chr)
             return -1;
 
+        qemu_chr_fe_claim_no_fail(chr);
         qemu_chr_add_handlers(chr, gdb_chr_can_receive, gdb_chr_receive,
                               gdb_chr_event, NULL);
     }