Add Average and Maximum classes

These classes will implement the
xyz.openbmc_project.Sensor.Aggregation.History.Average/Maximum
interfaces.   Each of these interfaces contains an array of
value/timestamp entries, where the value is either the average
or maximum power as reported by the power supply.  The most recent
value will always be in element 0 of the array.

Change-Id: I41b0b84abe146c57f23629bd50acbf9e7fb746ab
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/configure.ac b/configure.ac
index 9d38bcc..2ec466c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -30,6 +30,8 @@
     AC_MSG_ERROR(["Requires phosphor-logging package."]))
 PKG_CHECK_MODULES([PHOSPHOR_DBUS_INTERFACES], [phosphor-dbus-interfaces],,\
     AC_MSG_ERROR(["Requires phosphor-dbus-interfaces package."]))
+PKG_CHECK_MODULES([OPENPOWER_DBUS_INTERFACES], [openpower-dbus-interfaces],,\
+    AC_MSG_ERROR(["Requires openpower-dbus-interfaces package."]))
 # Check for sdbus++
 AC_PATH_PROG([SDBUSPLUSPLUS], [sdbus++])
 AS_IF([test "x$SDBUSPLUSPLUS" == "x"],