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/maxscaled/maxscaled.c

@@ -10,6 +10,9 @@
  * of this software will be governed by version 2 or later of the General
  * Public License.
  */
+
+#define MXS_MODULE_NAME "maxscaled"
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>