Add Sensor.Threshold server bindings

Temporarily add the server bindings for xyz.openbmc_project.Sensor.Threshold
until they are available elsewhere.

Change-Id: I476d0ee3abbc5a93a6720eedc4ecfa8ae0cc3d0c
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/Makefile.am b/Makefile.am
index ab4d373..1f5b6ca 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,6 +12,8 @@
 	sensorset.cpp \
 	mainloop.cpp \
 	sysfs.cpp \
-	xyz.openbmc_project.Sensor.Value.cpp
+	xyz.openbmc_project.Sensor.Value.cpp \
+	xyz.openbmc_project.Sensor.Threshold.Warning.cpp \
+	xyz.openbmc_project.Sensor.Threshold.Critical.cpp
 
 SUBDIRS = . test