Provide rf_AllocDAGNode() and rf_FreeDAGNode() to handle
allocation/freeing.
- Introduce a "nodes" linked list of RF_DagNode_t's into the DAG header.
Initialize nodes in InitHdrNode(). Arrange for nodes cleanup in rf_FreeDAG().
- Add a "list_next" to RF_DagNode_t to keep track of nodes on the
above "nodes" list. (This is distinct from the "next" field of
RF_DagNode_t, which keeps track of the firing order of nodes.)
"list_next" gets used in the cleanup routines, and in traversing
through a set of nodes that belong to a particular set of nodes
(e.g. those belonging to xorNodes for a given DAG).
- use rf_AllocDAGNode() instead of mallocs of variable-sized arrays of
RF_DagNode_t's. Mostly mechanical changes to convert the DAG construction
from "access nodes via an array index" to "access nodes via a 'nextnode'
pointer".
- rework a couple of tricky spots where assumptions about the node order
was being abused.
- performance remains consistent with performance before these changes.
[Thanks to Simon Burge (simonb at you.know.where) for looking over
the mechanical changes to make sure I didn't biff anything.]