Turn replaycache.c module doc into doxygen

src/or/replaycache.c

@@ -1,7 +1,7 @@
  /* Copyright (c) 2012-2016, The Tor Project, Inc. */
  /* See LICENSE for licensing information */
 
-/*
+/**
  * \file replaycache.c
  *
  * \brief Self-scrubbing replay cache for rendservice.c