Realized that, since html_() now returns a string, it's just as easy to
just pass that to fu->set_body(); no need for integration complexity.
Combined import options don't save much typing, not worth the overhead
either.
I initially planned to only implement the bare minimum to support
FastCGI under nginx, but ended up implementing the full protocol
instead. This is more code than I had expected and the code is also less
trivial than I had hoped. Will need to do more testing, pretty sure
there's bugs left.
Also TODO: test under alternative process managers + document
FU_LISTEN_PROTO.
I've also removed the max_request_body setting, this is something that
really ought to be configured in the web server instead.
A little tricky to get right, but it works pretty well.
TODO: Do something with --monitor.
I initially wanted to avoid the exec() and just let Perl continue
running the rest of the script after fork(), but that runs into the
problem that perl really doesn't like it when you fork() in BEGIN.
