include: Make headers iwyu-clean

Change-Id: Id5160c354e290f330f1ac94b41748288f42a1a7e
Signed-off-by: Peter Foley <pefoley@google.com>
diff --git a/include/sdbusplus/asio/sd_event.hpp b/include/sdbusplus/asio/sd_event.hpp
index 4a61a7c..249fd15 100644
--- a/include/sdbusplus/asio/sd_event.hpp
+++ b/include/sdbusplus/asio/sd_event.hpp
@@ -19,6 +19,7 @@
 
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/posix/stream_descriptor.hpp>
+#include <boost/asio/post.hpp>
 #include <boost/system/error_code.hpp>
 
 namespace sdbusplus
diff --git a/include/sdbusplus/slot.hpp b/include/sdbusplus/slot.hpp
index b91df69..6097bb6 100644
--- a/include/sdbusplus/slot.hpp
+++ b/include/sdbusplus/slot.hpp
@@ -2,6 +2,8 @@
 
 #include <systemd/sd-bus.h>
 
+#include <sdbusplus/sdbus.hpp>
+
 #include <memory>
 
 namespace sdbusplus
diff --git a/include/sdbusplus/utility/container_traits.hpp b/include/sdbusplus/utility/container_traits.hpp
index 5d14603..340a381 100644
--- a/include/sdbusplus/utility/container_traits.hpp
+++ b/include/sdbusplus/utility/container_traits.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <iterator>
 #include <utility>
 
 namespace sdbusplus