This file describes the old netlist model. The old model seems to be
deisgned from a GUI perspective, probably from the Xaw times. This old
model will eventually be replaced by a more proper tree structure that
will be able to represent hierarchic netlists.

Moved from the gtk sources:

    -------- The netlist nodes (pcb_lib_entry_t) data model ----------
    Each time a net is selected in the left treeview, this node model
    is recreated containing all the nodes (pins/pads) that are connected
    to the net.  Loading the new model will update the right treeview with
    all the new node names (C100-1, R100-1, etc).

    The terminology is a bit confusing because the PCB netlist data
    structures are generic structures used for library elements, netlist
    data, and possibly other things also.  The mapping is that
    the layout netlist data structure is a pcb_lib_t which
    contains an allocated array of pcb_lib_menu_t structs.  Each of these
    structs represents a net in the netlist and contains an array
    of pcb_lib_entry_t structs which represent the nodes connecting to
    the net.  So we have:

   |                      Nets              Nodes
   |       pcb_lib_t    pcb_lib_menu_t   pcb_lib_entry_t
   | -------------------------------------------------------
   |  PCB->NetlistLib------Menu[0]-----------Entry[0]
   |                     |                   Entry[1]
   |                     |                     ...
   |                     |
   |                     --Menu[1]-----------Entry[0]
   |                     |                   Entry[1]
   |                     |                     ...
   |                     |
   |                     -- ...
   |
   | Where for example Menu[] names would be nets GND, Vcc, etc and Entry[]
   | names would be nodes C101-1, R101-2, etc

