Bug#998513: Update on using "resolution WxH" instead of "resolution=WxH"

[Konstantin Khomoutov]

It turned out I was trying to specify the resolution in a wrong way -
using "resolution=WxH" instead of "resolution WxH".

Still, an attempt to start ROTT the correct way -

  $ rott-commercial window resolution 800x600

(with any supported width and height) fails in exactly the same manner,
as indicated in the original report.