- added support for macros with default arguments
- fixed bug where nested preprocessor conditionals would not be skipped
- macro expansion respects escaped quotation marks
- macro expansion considers whole identifiers, rather than substituting in wildly

This also entailed further fleshing out the expression traversal helper
to cover expressions in generate blocks, which could, of course, use
$bits.

- convert default pattern used to fill a vector
- convert Logic in parameter and localparam types
- interface conversion should happen early for type resolution later on
- interface conversion handles renaming of usages of inlined decls

don't prematurely unpack structs with complex types; support for convert patterns that use `default`

- unique0 and priority
- uniqueness on if statements
- preliminary discard-only parsing of assertions
- parameters with alias typenames

allow for stray semicolons in module items; allow for multiple struct field declarations on one line

This should make it much easier to add support for ``, `", macros with
arguments, etc., in the future.