ansi2html: add _write_form_feed
ansi2html: add _write_form_feed

Form feeds are rendered differently by HTML and text converters, so
move the HTML rendering out of _write_line's argument.

Signed-off-by: Paolo Bonzini <69d3ebcf5ee4e7f05a50dc23cd96655b730804b4@redhat.com>

patchew-project/patchew,patchew-project/patchew,patchew-project/patchew,patchew-project/patchew