- number literals are parsed rather than stored as strings
- fix array query functions used on non-trivial number literals
- more efficient expression simplification recursion
- expanded constant folding scenarios

- elaborated literals larger than 32 bits are given an explicit size
- constant folding no longer encodes illegal negative numbers

- modports can use complex expressions
- update interface_infer test for consistency across simulators
- fix interface inlining of implicitly typed data declarations

- removed repetition in dimension query conversion
- removed repetition in package item nesting conversion
- packing item nesting conversion short circuit
- param type conversion doesn't bother renaming non-param type instances
- implement showsPrec for certain expression cases

- single bit localparams retain explicit range
- fix $bits on unsized literals
- use Implicit over Maybe for underlying type

- constant folding supports hex numbers
- simplify mod
- simplify pow
- elaborate !(a == b) into a != b

Without this patch, a stray `endif caused sv2v to take the tail of an
empty list. Now we raise a lexical error.

To do this, the patch pulls the "push" and "pop" logic for the
preprocessor condition stack into separate helper
functions (pushCondStack and popCondStack). It also defines some
helper functions for manipulating Cond's.

The patch also adds a documentation comment explaining what the
different values of Code meant (because I had to squint to work it
out).

- adds support for using macros and macro arguments within the argument
  list to other macros
- fixes an issue where macros with arguments would have extraneous
  whitespace
- fixes handling of multiline string literals