Continue cleaning up shadowed variables, flagged by turning on -Wshadow.
No intended change in functionality. Patch looks right, and is tested
to compile and run on my machine. No regressions in test suite.
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.