unlike the previous hack, libgrapheme is UNICODE 15.0 compliant (at the time of writing) and provides some nice API. While here, drop the hard wrap method for preformatted blocks: always use the normal wrapping. Since libgrapheme is not yet widely available, future commits will probably add a bundled version to ease packaging. I'll also start to replace various home-grown UNICODE/utf8 handling routines with functions from libgrapheme.

it's currently unused (the net process unfortunately can't sensibly make use of it: breaks the DNS...) In the future I'd like to move the parsers in their own (sandboxed) process, so don't delete the landlock code yet.

The issue with building out-of-tree was that some pages were generated by autoconf in $(builddir) and others were as-in in $(srcdir). While it was possible to use the right combination of $(builddir)/$(srcdir), just move everything as .in and generate every page during the configure step.

fix use after free when loading an about:* page from about:about. Reported by Brian Callahan, thanks!