[krbdev.mit.edu #5440] sendto_kdc() not signal safe, doesn't respond well to staggered TCP responses.

[Ken Raeburn via RT]

After a little testing with a hacked KDC that sends back TCP responses in pieces with delays, I 
don't think that there is a problem with that part of the client code.

The library changes I've just checked in appear to fix the select/EINTR problem, so I'm going to 
mark this ticket as resolved.