some header bugs

[DJ Delorie]

> Bleah.  It looks like our version of setdtablesize takes an argument which
> is the amount to grow the fdtab by.  I found one use that assumed that
> the argument was the total size for the table.
> 
> It looks like bash wants this to be the total size, too.  Do you agree?

Yup.  I'm just commenting that call out in my code; it looks like the
easiest way to deal with the problem.