New tool Vfix: truncate the right edge of 'grey' type images to make

the scanline width a multiple of 4.

VFile: use gl.gversion() to distinguish 4.0.1 and 4.0.5 Indigos;
truncate width and height to multiples of packfactor.

Vinfo: add -t to descriptive comment; print '!' after packfactor for
files that should be fixed with Vfix.