Try to squelch the warning about not using the return value of strtoul()

Try to squelch the warning about not using the return value of strtoul()
- we really *are* using it just for its side-effects if it fails; its
return value is not the best way to check for failure, as the failure
return values are also valid return values on success.

While we're at it, check for it setting errno, which is one of the
better ways to check for failure.

svn path=/trunk/; revision=37606