Refactor: Relocated linknode_t from dd_share.h to m_nodepile.h

The node piles are no longer visible at API level so linknode_t can
now be moved out of dd_share.h

It is most likely that the node piles will be replaced entirely in
future (probably 1.13).

doomsday/api/dd_share.h

@@ -582,23 +582,6 @@ typedef struct traceopening_s {
 /// @defgroup mobj Map Objects
 /// @ingroup world
 
-/**
- * Linknodes are used when linking mobjs to lines. Each mobj has a ring
- * of linknodes, each node pointing to a line the mobj has been linked to.
- * Correspondingly each line has a ring of nodes, with pointers to the
- * mobjs that are linked to that particular line. This way it is possible
- * that a single mobj is linked simultaneously to multiple lines (which
- * is common).
- *
- * All these rings are maintained by P_MobjLink() and P_MobjUnlink().
- * @ingroup mobj
- */
-typedef struct linknode_s {
-    nodeindex_t     prev, next;
-    void*           ptr;
-    int             data;
-} linknode_t;
-
 /**
  * @defgroup stateFlags State Flags
  * @ingroup mobj

doomsday/client/include/m_nodepile.h

@@ -28,7 +28,22 @@
 
 #include "dd_types.h"
 
-struct linknode_s;                 // Defined in dd_share.h.
+/**
+ * Linknodes are used when linking mobjs to lines. Each mobj has a ring
+ * of linknodes, each node pointing to a line the mobj has been linked to.
+ * Correspondingly each line has a ring of nodes, with pointers to the
+ * mobjs that are linked to that particular line. This way it is possible
+ * that a single mobj is linked simultaneously to multiple lines (which
+ * is common).
+ *
+ * All these rings are maintained by P_MobjLink() and P_MobjUnlink().
+ * @ingroup mobj
+ */
+typedef struct linknode_s {
+    nodeindex_t     prev, next;
+    void*           ptr;
+    int             data;
+} linknode_t;
 
 typedef struct nodepile_s {
     int             count;