sdbusplus: use shorter type aliases

The sdbusplus headers provide shortened aliases for many types.
Switch to using them to provide better code clarity and shorter
lines.  Possible replacements are for:
  * bus_t
  * exception_t
  * manager_t
  * match_t
  * message_t
  * object_t
  * slot_t

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I6a559082fed34ae62b648345ead793436d2d03f6
diff --git a/src/pathwatch.hpp b/src/pathwatch.hpp
index bc0cb3a..d9bb836 100644
--- a/src/pathwatch.hpp
+++ b/src/pathwatch.hpp
@@ -54,7 +54,7 @@
      *
      *  Watch callback interface implementation for PathWatch.
      */
-    void callback(Context ctx, sdbusplus::message::message& msg) override;
+    void callback(Context ctx, sdbusplus::message_t& msg) override;
 
   protected:
     /** @brief Path of the D-Bus object to watch for. */