now it's symmetrical to listener_main().

FRC3875 says that if the query does not contain any unecnoded "=" characters, we SHOULD treat the query string as a "search-string", split in on "+" and add every word to the CGI argv. In launch_cgi it's too late because iri->query is the *decoded* query! I have in mind some refactoring around how we decode things, so this is postponed.

Oh my, this is such a stupid mistake. It went undiscovered only because I always used CGI scripts on the first vhost (and hence the offset would be 0) and never on the others.

while there also add SERVER_PROTOCOL

when we switched from one process to two, I introduced a small optimisation: empty string are not send, so we receive NULL. Constructing requri we need to make sure that relpath is not null.