Revert "another checkpoint in big df entity elimination pass"

This reverts commit f8fd32e328.

src/mdesk/mdesk.h

@@ -169,6 +169,8 @@ struct MD_Node
   MD_Node *parent;
   MD_Node *first;
   MD_Node *last;
+  
+  // rjf: tag links
   MD_Node *first_tag;
   MD_Node *last_tag;
   
@@ -180,9 +182,6 @@ struct MD_Node
   
   // rjf: source code info
   U64 src_offset;
-  
-  // rjf: user-controlled data attachments
-  U64 user_gen;
 };
 
 typedef struct MD_NodeRec MD_NodeRec;