- use iverilog's -gstrict-expr-width throughout test suite
- add warnings for excess bits or padding zeroes in number literals
- add new --oversized-numbers parameter to retain support for unsized
  numbers wider than 32 bits
- localized use of oversized numbers to new truncate test suite which
  verifies the behavior of both modes, and compares against the known
  behavior of iverilog

- add unified frontend configuration record to make adding future
  options easier
- use ExceptT throughout, rather than using runExceptT at internal
  boundaries

- Trace comments cover module items, decls, and stmts
- Added pseudo-lexer to Alex parser for monadic Position production
- Added Position to every DeclToken
- Removed Comment PackageItem
- Added CommentStmt and CommentDecl
- Fixed traversal skipping outer MIAttr ModuleItems
- Generally cleaned up Parser modules

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