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/protocol/MySQL/MySQLBackend/mysql_backend.c

@@ -11,6 +11,8 @@
  * Public License.
  */
 
+#define MXS_MODULE_NAME "MySQLBackend"
+
 #include <maxscale/protocol/mysql.h>
 #include <maxscale/log_manager.h>
 #include <maxscale/modutil.h>