[plugins] director: fixes director.fcgi()'s just added client-abort mode feature
[http] HttpRequest: exposes abort() in order to hard-close a connection and thus kill its currently processed request
[x0d] redirect() and respond() have been both redesigned and renamed into return() to be more familiar with nginx configuration
[base] io/*: generalize Source::size() and do a minor code polishing wrt. std::unique_ptr<> use
yo, belongs to last io/* commit
[plugins] director: makes use of consumeBody() call to defer backend allocation.
[plugins] director: passes client auth'd username to fcgi backend
[x0d] header.*() methods improved to apply their actions right before the headers get serialized
[plugins] director: http backend now properly handles file-accel for response processing and makes also use of O_TMPFILE if available/enabled.
[plugins] director: make use of O_TMPFILE in fastcgi backend now, too.