Add new parameter to optionally enable Out-Of-Band for a QMP server.
An example command line:
./qemu-system-x86_64 -chardev stdio,id=char0 \
By default, Out-Of-Band is off.
It is not allowed if either MUX or non-QMP is detected, since
Out-Of-Band is currently only for QMP, and non-MUX chardev backends.
Note that the client STILL has to request 'oob' during qmp_capabilities;
in part because the x-oob command line option may disappear in the
future if we decide the capabilities negotiation is sufficient.
Signed-off-by: Peter Xu <firstname.lastname@example.org>
Reviewed-by: Marc-André Lureau <email@example.com>
[eblake: enhance commit message]
Tested-by: Christian Borntraeger <firstname.lastname@example.org>
Signed-off-by: Eric Blake <email@example.com>