Bug 1246931: Include dbus.h in DBus IPC headers, r=shuang

The header files for DBus IPC forward declare several DBus types in
a way that interferes with the actual declarations. It's better to
include the DBus headers directly

ipc/dbus/DBusUtils.h

@@ -19,6 +19,7 @@
 #ifndef mozilla_ipc_dbus_dbusutils_h__
 #define mozilla_ipc_dbus_dbusutils_h__
 
+#include <dbus/dbus.h>
 #include "mozilla/RefPtr.h"
 
 // LOGE and free a D-Bus error
@@ -26,9 +27,6 @@
 #define LOG_AND_FREE_DBUS_ERROR_WITH_MSG(err, msg) log_and_free_dbus_error(err, __FUNCTION__, msg);
 #define LOG_AND_FREE_DBUS_ERROR(err) log_and_free_dbus_error(err, __FUNCTION__);
 
-struct DBusError;
-struct DBusMessage;
-
 namespace mozilla {
 namespace ipc {