linux clears dumpable flag on uid change

[Ryan Melendez]

> Patches are always welcome.  :)
> 
> Please file it at bugs.freeradius.org.
> 

http://bugs.freeradius.org/show_bug.cgi?id=361

I'd like to see this included in a future release.  Please let me know
if I can to anything to improve the patch. I am willing to work at it to
make it worthy.

Thanks,
Ryan