Rename skygw_debug.h to debug.h

Also remove unneded includes in debug.h

server/modules/routing/avro/avro_index.c

@@ -33,7 +33,7 @@
  */
 
 #include "avrorouter.h"
-#include <maxscale/skygw_debug.h>
+#include <maxscale/debug.h>
 #include <glob.h>
 
 void* safe_key_free(void *data);