example: add client API example

Create a small application which calls org.freedesktop.login1
to display a list of the active users.

Change-Id: I8d7879d98f6b89a9315aa0c71b928c50490dfedb
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/example/Makefile.am b/example/Makefile.am
index 8d38538..ae5cdcb 100644
--- a/example/Makefile.am
+++ b/example/Makefile.am
@@ -1,4 +1,4 @@
-noinst_PROGRAMS = calculator-server
+noinst_PROGRAMS = calculator-server list-users
 
 calculator_server_generated_files = \
 	net/poettering/Calculator/server.hpp \
@@ -14,6 +14,10 @@
 calculator_server_CXXFLAGS = $(SYSTEMD_CFLAGS)
 calculator_server_LDADD = $(SYSTEMD_LIBS) ../libsdbusplus.la
 
+list_users_SOURCES = list-users.cpp
+list_users_CXXFLAGS = $(SYSTEMD_CFLAGS)
+list_users_LDADD = $(SYSTEMD_LIBS) ../libsdbusplus.la
+
 BUILT_SOURCES = \
 	$(calculator_server_generated_files) \
 	$(calculator_markdown_generated_files)