listener: adding quiet mode.
listener: adding quiet mode.

This skips printing the version info when starting the listener.

    ./factor -q
    ./factor -q -run=listener
    ./factor -q -run=readline-listener

mrjbq7/factor,AlexIljin/factor,factor/factor,AlexIljin/factor,tgunr/factor,bpollack/factor,mrjbq7/factor,AlexIljin/factor,factor/factor,bpollack/factor,mrjbq7/factor,AlexIljin/factor,tgunr/factor,factor/factor,mrjbq7/factor,AlexIljin/factor,factor/factor,factor/factor,tgunr/factor,bpollack/factor,bpollack/factor,AlexIljin/factor,bpollack/factor,factor/factor,AlexIljin/factor,mrjbq7/factor,tgunr/factor,mrjbq7/factor,tgunr/factor,tgunr/factor,bpollack/factor,bpollack/factor