These are now kept while still supporting optional trailing commas and
without introducing pass-through inconsistencies.

- fold string literal comparisons
- fold non-decimal bit shifts
- fold non-decimal integer comparisons
- fold decimal bitwise AND and OR
- simplify cast expressions before elaboration
- remove duplicate cast expression traversal
- flatten concatenated numbers in a single pass

- scoped traversals can now raise errors which contain the path of the
  current scope and an approximate source location based on preceding
  trace comments, if available
- initially, this new error messaging has only been added for the
  illegal size cast checks in the TypeOf and Cast conversions
- error suite tests can provide a verbose mode expected source location

- error suite runs in both regular and verbose mode
- add helper for extracting "flags" from test files
- common assertMatch, assertNotMatch helpers
- remove unused assertExists helper
- fix un-escaped wildcard in assert_deferred_nonzero.sv

Specifically, support has been added for non-ANSI style port
declarations where the port declaration is separate from the
corresponding net or variable declaration.

This adds support for typed valued parameters declared in parameter port
lists without explicitly providing a leading `parameter` or `localparam`
marker.

- detect and forbid non-positive size casts
- detect and forbid negative struct pattern literal indices
- avoid invalid constant folding of negative based literals

- references to other instances are no longer flagged
- special handling for genvars to avoid flagging and modport scoping
- interface inlining visits expressions in declarations
- Scoper has interface for removing entries

- general refactoring in decl parsing
- restrict charge strength to trireg
- require const vars to be initialized
- forbid const net declarations
- disallow run-on declarations in packages and classes

- remove outdated flexible partial type eq and show instances
- properly disallow incomplete declarations
- disallow var after net type
- remove unused edge case in InterfaceT representation

- support for additional assignment statements in loop initializations
- greatly improved error messaging in these contexts
- decl parser takes in the ending token; significant related refactoring
- pass through elaboration system tasks
- removed non-blocking assignment operator precedence hack
- preliminary nosim test suite for features unsupported by iverilog

- all decl tokens are given an accurate starting position
- key grammar productions return token positions to facilitate the above
- helpers for standardized parse error generation
- replaced annoying pattern-matching type argument restrictions
- moving away from dumping raw decl tokens in error messages

- pattern keys now represented as TypeOrExpr
- support for simple integer struct pattern keys

- disallow using end label alone on blocks
- improved parse error for mismatches
- add label checking for non-block constructs
- allow generate block to have label before begin

- fix type/expr ambiguity for interface and class parameters
- check for parameter kind mismatch up front
- centralize key logic in ResolveBindings