- variable-size string parameter conversion restricted to modules which
  depend on the size of the string parameter
- string localparams are typed as appropriately sized vectors
- remove ordered parameter binding logic from string param conversion

- `expr.name[idx]` considers `expr.name` could be a struct array
- remove fallback struct type lookups which were guaranteed to fail

- preproc reads identifiers unconditionally
- drop leading whitespace for default macro args
- very minor preproc cleanup

- fix preservation of loop variables when breaking
- extend Yosys-compatible constant loop conversion to support loop
  variables declared outside of the looop

- avoid premature conversion of default struct type parameters
- allow use of $clog2, $signed, and $unsigned in type parameters
- more thorough and efficient top reference ident renaming
- precede type param conversion with hier const pass

- renaming applies to nodes within generate blocks
- renaming applies to LHSs