monitor: Add thermal fault alert D-Bus property

Add a new property to alert of a thermal fault.  In this context, it
means an imminent power off due to fan faults.  On certain IBM systems
it will be used as a mechanism to alert the host of the power off when
the 'epow_power_off' power off rule is used.

Service: xyz.openbmc_project.Thermal.Alert
Path: /xyz/openbmc_project/alerts/thermal_fault_alert
Interface: xyz.openbmc_project.Object.Enable
Property: Enabled

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I0531de9ce40b6148244fda18a20e144bad85d830
diff --git a/monitor/system.hpp b/monitor/system.hpp
index 744c775..a0030da 100644
--- a/monitor/system.hpp
+++ b/monitor/system.hpp
@@ -146,6 +146,11 @@
     std::unique_ptr<FanError> _lastError;
 
     /**
+     * @brief The thermal alert D-Bus object
+     */
+    ThermalAlertObject _thermalAlert;
+
+    /**
      * @brief Captures tach sensor data as JSON for use in
      *        fan fault and fan missing event logs.
      *