add load-url-use-heuristic knob This is still WIP and may change before the next release. It could be worthwile to resolve the URLs in load-url using the current page as base, so that while browsing <gemini://a.org/b/c>, using load-url to go to "/" would load <gemini://a.org/> instead of <file:///>. The new option `load-url-use-heuristic', if unset, provides exactly this behaviour. It is still a bit rough to use, as for e.g. loading <d.net> would now yield <gemini://a.org/b/d.net> instead of <gemini://d.net>. Will need more work in-tree, but for now add it so we can reason about it. See github issue #10

move headers to include/