[usrmarshal] Adjust new tests to pass on win9x platforms.

[Jeremy White]

> It looks like a good place to use broken().

I don't think it's broken on win98; it looks as though
they do 4 byte alignment prior to the data structure in win9x, 
and winnt and on seem to do 8 byte alignment prior to the
data chunk.  That results in a 4 byte difference.

Cheers,

Jeremy