Revert "st.c: use ccan linked-list (try 2)"

This reverts commit r51044
Still getting failure notices from ko1's CI machine.
ref: g3qkqn

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51045 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,26 +1,3 @@
-Sat Jun 27 06:58:01 2015  Eric Wong  <e@80x24.org>
-
-	* include/ruby/st.h (struct st_table): hide struct list_head
-	* st.c (struct st_table_entry): adjust struct
-	  (head, tail): remove shortcut macros
-	  (st_head): new wrapper function
-	  (st_init_table_with_size): adjust to new struct and API
-	  (st_clear): ditto
-	  (add_direct): ditto
-	  (unpack_entries): ditto
-	  (rehash): ditto
-	  (st_copy): ditto
-	  (remove_entry): ditto
-	  (st_shift): ditto
-	  (st_foreach_check): ditto
-	  (st_foreach): ditto
-	  (get_keys): ditto
-	  (get_values): ditto
-	  (st_values_check): ditto
-	  (st_reverse_foreach_check): ditto (unused)
-	  (st_reverse_foreach): ditto (unused)
-	  [ruby-core:69726] [Misc #10278]
-
 Fri Jun 26 12:48:37 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* transcode.c (load_transcoder_entry): fix transcoder loading race

include/ruby/st.h

@@ -86,7 +86,7 @@ struct st_table {
     union {
 	struct {
 	    struct st_table_entry **bins;
-	    void *private_list_head[2];
+	    struct st_table_entry *head, *tail;
 	} big;
 	struct {
 	    struct st_packed_entry *entries;