Tran islands are a kinds of island, so seperate the tran handling
from the core island concept. This will allow for creating new
kinds of islands. (Think analog.)
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