Recursive branch resolution was scanning every branch end, even though
many branch ends share ports and need not be repeatedly scanned. Handle
marks and flags to cut off recursion where it is not needed so as to
save much run time.
Fold the bi-directional part select into the pass switch (tran) support
so that it can be really bi-directional. This involves adding a new
tranvp device that does part select in tran islands, and reworking the
tran island resolution to handle non-identical nodes. This will be needed
for resistive tran devices anyhow.
The vvp_island classes are added, as well as support for tranif nodes
that use this concept. The result is a working implementation for
tranif0 and tranif1.
In the process, the symbol table functions were cleaned up and made
into templates for better type safety, and the vvp_net_ptr_t was
generalized so that it can be used by the branches in the island
implementation.
Also fix up the array handling to use the better symbol table support,
and to remember to clear its own table when linking is done.
Stephen Williams