Fix format string, include and other minor stuff

[gsauthof]

This pull request fixes a format string, replaces the forward declaration with the right include and fixes the indentation.

[CLAassistant]

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[gsauthof]

I don't think that this contribution achieves the 'threshold of originality' (when it comes to copyright).

I'm not a lawyer and I really don't have time to read your fine Contributor License Agreement.

Thus, I'm not going to sign it.

If you really think that this is obstacle because you assume that the threshold of originality is reached I'm willing to license my contribution under a very permissive license like the MIT-0 (which doesn't even require attribution) and/or release it into the public domain.

[artemdinaburg]

I just saw this was here :). The CLA bot is on for everything so I can't merge your contribution directly, but this is GPLv2 anyway so I will gladly incorporate the small fixes as a separate commit.