Add definitions of MXS_MODULE_NAME to all modules

All modules now declare a name for the module. This is name is added as a
prefix to all messages logged by a module. The prefix should help
determine which part of the system logs a message.

server/modules/routing/avrorouter/avrorouter.h

@@ -18,6 +18,9 @@
  * MaxScale AVRO router
  *
  */
+
+#define MXS_MODULE_NAME "avrorouter"
+
 #include <maxscale/cdefs.h>
 #include <stdbool.h>
 #include <stdint.h>