Changed the parameter 'char * data' of process_start to the

type process_data_t. This was an artifact when the choice was
made to use the void * type for the data parameter in processes.

Changed parameter 'void * data' of process_post_synch to
process_data_t for consistency.

Checked all the uses of process_start() in contiki and fixed casts
of the data parameter.

core/loader/dlloader.c

@@ -62,7 +62,7 @@ dlloader_load(char *path, char *arg)
   /* Start the process. */
  
   printf("Starting '%s'\n", PROCESS_NAME_STRING(*p));
-  process_start(*p, arg);
+  process_start(*p, (void *)arg);
 
   return LOADER_OK;
 }