'nohup' seems to be broken in Cygwin git master

[Mark Geisert]

Easiest way I have to reproduce is using X.  In a Cygwin terminal enter:
     nohup xlogo &
     exit

The terminal window and xlogo are both terminated.  With gdb I see that 
xlogo terminates with STATUS_CONTROL_C_EXIT.

On a 32-bit 3.1.4 install, same machine, same (64-bit 3.1.pre5) X server, 
the same test case shows the terminal window terminated but xlogo remains.

X is not required to demonstrate this; it's just easiest way to see the 
effect.  I can dig further if this doesn't immediately pique someone's 
interest... :)

..mark