try and be a bit more standard

ds.h

@@ -1,14 +1,14 @@
-#ifndef _DS_LOADED
-#define _DS_LOADED
+#ifndef DS_H
+#define DS_H
 
-typedef struct _sll {
-  struct _sll *next;
+typedef struct _ds_sll {
+  struct _ds_sll *next;
   void        *data;
 } ds_sll_t;
 
-typedef struct _dll {
-  struct _dll *next;
-  struct _dll *prev;
+typedef struct _ds_dll {
+  struct _ds_dll *next;
+  struct _ds_dll *prev;
   void        *data;
 } ds_dll_t;