Hurd's defpager and memory leak bugs

[Igor Khavkine]

Is Hurd's `defpager' used at all? Is it even compiled while building
the Hurd? [hurd]/defpager/defpager.c contains a blatant bug that
should not even compile. But if `defpager' completely ignored, that
could be ignored as well.

Also, I took a look at the current Hurd source tree and noticed that
a lot of the fixes for null-from-malloc or no-free-after-malloc
type bugs that I posted a while ago. I remember there were some
concerns about propagation of error in certain situations. I can
look through these fixes again and make sure that reported errors
are propagated properly, etc. Also I can repost them in smaller
batches so it would be easier to review them. How many do you want,
a dozen, two dozen at a time?

Igor