working of footer/header first/even/odd is changed

[Klap-in]

Now:
Writer::applyHeaderFooters()

• On first call it adds the footer first or header first for the first wiki page (if not defined, it falls back to general footer/header if defined)
• on the next calls it adds the (odd/even) footers and headers for the following wiki pages.

Before:

$styles = '@page { size:auto; ' . $template['page'] . '}';
$styles .= '@page :first {' . $template['first'] . '}';

The @page :firstselector had a smaller reach, just one page of the pdf.
While if you have no cover page, the applyHeaderFooters() is called once, such that for an export with one wiki page, only the header_first/footer_first is written. If a cover.html is available, then applyHeaderFooters() is called a second time and also the not-first headers (odd/even) are written.

I wonder if the runtime mode (which is used now instead of the named mode which could be referred with @page) has a option for only having other headers for the first page of the pdf, I think not. (if read it correctly @page overrides the others, so mixing will not help).

Alternative is to use footer/header first explicitly only for if the cover page is defined?

• regarding backward compatibility: No idea how many people are using first footer/headers ...
• When connecting only to the cover, it is probably also more clear to rename it to footer/header cover? (and add footer/header back as well?

[btw: from reading the docs, I guess footer/headers in runtime mode around a ToC might have also potential issues. I could not yet grep what the docs exactly mean. But not tested.]