- "Double quotes" for strings (filenames, section names, CLI option arguments, etc)
- 'Single quotes' for characters and CLI option flags
- `Backticks` for keywords and identifiers (symbol names, charmap names, etc)
CLI option flags also have their leading dashes
Expanding empty strings is valid but pointless;
macro args already skipped doing so, now other
`beginExpansion` calls do too.
This also fixes failed interpolations (which were
already non-fatal) to continue reading characters,
not evaluate to their initial '{' character.
This should significantly improve performance: on pokecrystal builds, perf
reported as much CPU time spent on `yyparse` as on `sym_UseNewMacroArgs`
Measurements show ~6 seconds of improvement on that codebase.
This also fixes#321, as a bonus, due to saner management!
