the username-for-accounting field (P), not the username-for-headerpage (L).
These are usually the same value, except that control files do not have
the username-for-headerpage field if the user has requested no header page.
- Also rename the cji_username field to cji_headruser, to make it clear that
the value should only be used for the header page. (aka banner page)
MFC after: 3 weeks
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