[cgi] split the query in words if needed and add them to the argv

use log_err instead of fprintf

ensure CGI stdout it's blocking

reload configuration on SIGHUP

refactor executor_main now it's symmetrical to listener_main().

[cgi] always set some variables

don't add the query to argv 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.

bring the CGI implementation in par with GLV-1.12556

fix computed offset 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.

unveil x the vhosts directories

sync the CGI environment with the manpage while there also add SERVER_PROTOCOL

pass the fd, not the path!

chdir to the vhost root before exec'ing the CGI script

don't leak file descriptors