using module 'jpeg' by the Displayer class.  (Unfortunately it's too
slow for real time.)  Print file size in printinfo() method.

Vinfo: added -t option (terse -- one line per file) and usage message.

Vtime: use BasicV{in,out}File classes -- the minimum needed.

Vmkjpeg, Vunjpeg: new utilities for jpeg (de)compression.