- "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
- Single unified routine for erroring out or handling missing dependencies
- Single three-state enum instead of two Booleans for missing dependencies
(this causes `-MC` to imply `-MG` instead of needing `-MG -MC`)
- Functions than can miss included files return a Boolean for whether the
parser should `YYACCEPT` and exit
Part of that condition's purpose is to ensure that we read the correct
lexer state; but it's possible now for the fstack to be non-empty
*before* the lexer state is registered, i.e. if there is an error
in the function that registers it.
This causes a NULL pointer deref.
