Fix select() multiplexer: possible fd lossage in RECALC-FD-MASKS.
Fix select() multiplexer: possible fd lossage in RECALC-FD-MASKS.

dkochmanski/iolib,lispnik/iolib,tiago4orion/iolib,tiago4orion/iolib,deadtrickster/iolib,sionescu/iolib,deadtrickster/iolib,attila-lendvai/iolib,tiago4orion/iolib,shamazmazum/iolib,dkochmanski/iolib,sionescu/iolib,attila-lendvai/iolib,dkochmanski/iolib,shamazmazum/iolib,attila-lendvai/iolib,vsedach/iolib-simple-mux,lispnik/iolib,vsedach/iolib-simple-mux,sionescu/iolib,deadtrickster/iolib,lispnik/iolib,shamazmazum/iolib