PEL: Add HostNotifier class

This class will watch for new PELs being created, and handle sending
them up to the host.  This first commit for this class mostly just fills
in the constructor to set up the various callbacks it will use.

It is only instantiated in the Manager class if the Manager constructor
used is the one that passes in the HostInterface object, to allow for
configurations that don't need PELs passed up.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I0ddcf94d047979eb78209d396c2351566c634dbe
diff --git a/extensions/openpower-pels/openpower-pels.mk b/extensions/openpower-pels/openpower-pels.mk
index f028293..220668f 100644
--- a/extensions/openpower-pels/openpower-pels.mk
+++ b/extensions/openpower-pels/openpower-pels.mk
@@ -1,5 +1,6 @@
 phosphor_log_manager_SOURCES += \
 	extensions/openpower-pels/entry_points.cpp \
+	extensions/openpower-pels/host_notifier.cpp \
 	extensions/openpower-pels/manager.cpp \
 	extensions/openpower-pels/repository.cpp \
 	extensions/openpower-pels/user_data.cpp