Rename SLIST_ENTRY to TOR_SLIST_ENTRY to fix windows compilation

Apparently winnt.h defines a different SLIST_ENTRY of its own.

Bug not in any version of Tor.

src/ext/tor_queue.h

@@ -99,7 +99,9 @@ struct name {								\
 #define	SLIST_HEAD_INITIALIZER(head)					\
 	{ NULL }
  
-#define SLIST_ENTRY(type)						\
+/* XXXX This macro name conflicts with a typedef in winnt.h, so Tor
+ * has to redefine it. */
+#define TOR_SLIST_ENTRY(type)						\
 struct {								\
 	struct type *sle_next;	/* next element */			\
 }