[Dillo-dev] Splitting html.cc: common functions, part 1

This patch moves some function declarations from html.cc to html_common.hh . It only does *some* of the renaming because the full patch breaks the list's moderation limit. I'll follow up to this message with the rest of the renaming. You may want to batch this patch and the followup together as a single commit. Please comment! Jeremy Henty