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!

pagebundler is a helper that needs to be built with the *host* compiler because it's used to generate some sources. In normal situations, HOSTCC and HOSTCFLAGS are just ${CC} and ${CFLAGS}, but folks that cross-compile can specify there the host compiler and flags to successfully build telescope. The idea is largely based on what gforth does: it re-uses ${CFLAGS} for the host compiler though, while I'm adding an extra variable for that.