Change sigTTOU/TTIN to IGNORE by default

[Simon Marlow]

> So it seems that there is possibly a feature/bug in the C library
> such that calling tcsetattr() always suspends a backgrounded process,
> regardless of the setting of TOSTOP.  As yet, I haven't been able to
> find a workaround.  :-(

Yes, I went through a similar set of diagnoses myself after I sent the
earlier message.  You can set the TOSTOP flag with stty in the shell,
and have the C program invoke system("stty") to see what's actually set.

It's particularly weird that Linux & Solaris behave identically.
Perhaps bug-for-bug compatibility has crept in?   

Cheers,
	Simon