The NetBranch object is connected, but not like an object, so the
NetPins object base class is factored out from NetObj to handle the
connectivity, and the NetBranch class uses the NetPins to connect a
branch.
Also, account for the fact that nets with a discipline are by default
real-valued.
Detect function call expressions that turn out to be calls to the
access function of a nature. Elaborate the access function and stub
the emit code. This gets the access function just short of the code
generator.
Pform parse enough of the natures that they can be mapped and the
disciplines can bind to them. Since Verilog-AMS expects natures to
be declared before use, we can do the binding early.
Parse discipline declarations, net discipline declarations, and
analog contribution statements. Don't yet do anything useful with
these, just give a sorry message where they are encountered.