patch to russian-rev: more railroads

[Jim Kingdon]

> If you have tested it and it works I would say put it up.

Well, it is better than without, so I've checked it in.  I wasn't
trying to make it reflect Russia as such, it was more a matter of
trying to balance things out so that fleets and railroads each have a
role (not sure I really succeeded, though).

However, playing feb-1917.g does give me a new perspective - this is a
*big* world, with long railroads and wide open plains (good for
calvary).  So I've put in a comment in russian-rev.g mentioning the
issue of world size.