Remove unused field

lib/nghttp2_map.c

@@ -130,7 +130,6 @@ int nghttp2_map_each(nghttp2_map *map,
 
 void nghttp2_map_entry_init(nghttp2_map_entry *entry, key_type key) {
   entry->key = key;
-  entry->next = NULL;
 }
 
 /* FNV1a hash */

lib/nghttp2_map.h

@@ -40,12 +40,11 @@
 typedef int32_t key_type;
 
 typedef struct nghttp2_map_entry {
-  struct nghttp2_map_entry *next;
-  key_type key;
-#if SIZEOF_INT_P == 4
-  /* we requires 8 bytes aligment */
-  int64_t pad;
-#endif
+  union {
+    key_type key;
+    /* we requires 8 bytes aligment */
+    int64_t pad;
+  };
 } nghttp2_map_entry;
 
 typedef struct nghttp2_map_bucket {