fetch resume support

[Frank Laszlo]

I was thinking about this the other evening when I recieved an email 
from Trevor Johnson about the SIZE now incorporated into the distinfo. 
With this in place, it would be quite easy to add support for resumable 
distfile fetching. I would be more than happy to write a patch for 
bsd.port.mk for this, but I would like to see how the community responds 
to it. What do you all think?

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Frank Laszlo
VonOstin Group
laszlof at vonstingroup dot com