Qemu creates a default parallel port for you in case you didn't specify
one on the command line.  Right now this is tied to the '-parallel
<chardev>' command line switch, which in turn causes trouble if you are
creating your parallel port via '-device isa-parallel,<props>'.

This patch adds a variable default_parallel which says whenever a default
parallel port should be added.  It is enabled by default.  It is cleared
when qemu finds '-parallel' or '-device isa-parallel' on the command line.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>