Lua odkim.del_header function ignores header number

[branciar]

The odkim.del_header(ctx, name, n) function offered for use in Lua final script is broken:
it always deletes the first instance of the provided header instead of the nth one.

The attached patch is a fix proposal.
opendkim_dkimf_xs_delheader_patch.txt

[futatuki]

I'm interested in the issue because I'v used Lua script in setup. However your patch cannot be gotten from Github. Could you make a PR address it, or gist for the patch, or something that those who is interested in it can see?

[futatuki]

... However your patch cannot be gotten from Github. ...

Ah, it was temorary error, and I could get the patch.

[futatuki]

I conformed it. I think you are right.

[futatuki]

I made PR #206 for going ahead.

[futatuki]

@branciar If you will make a PR address this issue by yourself, I'll close PR #191.