tab characters (U+0009) in \d-code block

[nyuichi]

Tab characters in \d-code block are not displayed correctly.

For the following code,

@require: stdjareport
@require: code

document (|
  title = {\SATySFi;};
  author = {Nanashi Taro};
|) '<
  % delimited by tabs
  \d-code(`
  key	value
  1	apple
  2	orange
  3	pear
  `);
}
>

satysfi generates

with warnings:

$ satysfi test.saty
[...]
 ---- ---- ---- ----
  evaluating texts ...
  [Warning] No glyph is provided for U+0009 by font `lmmono`.
  [Warning] No glyph is provided for U+0009 by font `lmmono`.
  [Warning] No glyph is provided for U+0009 by font `lmmono`.
  [Warning] No glyph is provided for U+0009 by font `lmmono`.
  evaluation done.
 ---- ---- ---- ----
[...]