`-fd-lines-as-code` and `-fd-lines-as-comments` enables treatment for
lines beginning with `d` or `D` in fixed form sources.
Using these options in free form has no effect.
If the `-fd-lines-as-code` option is given they are treated as if the
first column contained a blank.
If the `-fd-lines-as-comments` option is given, they are treated as
comment lines.
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