score: Add debug support to chains

This helps to detect

 * double insert, append, prepend errors, and
 * get from empty chain errors.

cpukit/sapi/include/rtems/chain.h

@@ -187,6 +187,21 @@ RTEMS_INLINE_ROUTINE void rtems_chain_set_off_chain(
   _Chain_Set_off_chain( node );
 }
 
+/**
+ * @brief Initializes a chain node.
+ *
+ * In debug configurations, the node is set off chain.  In all other
+ * configurations, this function does nothing.
+ *
+ * @param[in] the_node The chain node to initialize.
+ */
+RTEMS_INLINE_ROUTINE void rtems_chain_initialize_node(
+  rtems_chain_node *node
+)
+{
+  _Chain_Initialize_node( node );
+}
+
 /**
  * @brief Is the node off chain.
  *

cpukit/sapi/include/rtems/rbheap.h

@@ -210,6 +210,7 @@ static inline void rtems_rbheap_add_to_spare_descriptor_chain(
   rtems_chain_control *chain =
     rtems_rbheap_get_spare_descriptor_chain(control);
 
+  rtems_chain_initialize_node(&chunk->chain_node);
   rtems_chain_prepend_unprotected(chain, &chunk->chain_node);
 }
 

cpukit/sapi/src/rbheap.c

@@ -76,6 +76,7 @@ static void add_to_chain(
   rtems_rbheap_chunk *chunk
 )
 {
+  rtems_chain_initialize_node(&chunk->chain_node);
   rtems_chain_prepend_unprotected(chain, &chunk->chain_node);
 }