SrcBlock/NativeIndent demonstrates native indentation

[TobiasZawada]

Hi @bbatsov,
the branch SrcBlock/NativeIndent demonstrates native indentation in code blocks by indent-for-tab-command in a corresponding language buffer.

[bbatsov]

Nice! Please, open a PR about it as well, so it's easier to leave feedback about it.

[TobiasZawada]

The source blocks themselves are not the problem. The problem is the other stuff.
And indentation is (pityingly) such an all-or-nothing-thing (indent-line-function).

On this field one needs to consider quite a lot of adoc-spec.