The new field will allow error handling to be configured by
qdev_prop_register_global() callers: &error_fatal and
&error_abort can be used to make QEMU exit or abort if any errors
are reported when applying the properties.

While doing it, change the error message from "global %s.%s=%s
ignored" to "can't apply global %s.%s=%s".
Suggested-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>