[mod_magnet] expose r->keep_alive to lua scripts
[mod_magnet] expose r->keep_alive to lua scripts

lighty.r.req_item.keep_alive

Allow lua scripts to set to 0 or -1.  Setting to -1 might be used when
rejecting authentication, and this value will cause lighttpd to delay
the 401 Unauthorized response if the server feature is enabled (default)
  server.feature-flags += ("auth.delay-invalid-creds" => "enable")

gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4