In places where an optional space was previously allowed, allow any
number of arbitrary whitespace characters, in line with the spec and
other tools.

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

- 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

- 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