Monitor.flags contains three different flags: One to distinguish HMP
from QMP; one specific to HMP (MONITOR_USE_READLINE) that is ignored
with QMP; and another one specific to QMP (MONITOR_USE_PRETTY) that is
ignored with HMP.

Split the flags field into three bools and move them to the right
subclass. Flags are still in use for the monitor_init() interface.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20190613153405.24769-14-kwolf@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>