For source-level debug. Add --line-directives option, defaulted to
statement. Disabled when used with -C. Explicit non-none value
overrides disabling when -C is present
Prior to the fix, the Sex code
`(while (!= EOF (= c (getc f))) ...)` expanded wrongly to
`while (EOF != c = getc(f)) { ...`, instead of
`while (EOF != (c = getc(f))) { ...`
Also rename macros to sex-macros, module-system to sex-modules for
clarity, uniformity, and to avoid name clashes with Chicken's
units/modules named "macros" and "modules"
