Fix zone garbage collector to support PCH

[Geoff Keating]

Ian Lance Taylor <ian@wasabisystems.com> writes:

> I don't know why ggc-page.c bothers to page align the file pointer.
> The file is just being used for fread() and fwrite() of sizes which
> appear to normally be less than a page.  I can't see why aligning the
> file pointer provides any benefit, and it obviously makes the
> resulting PCH file a bit larger.  However, I didn't try to change
> that.

I believe it's to make mmap work better.  It certainly makes it more
efficient, I'm not sure if there aren't platforms where mmap doesn't
work at all if you don't do this.

-- 
- Geoffrey Keating <geoffk@geoffk.org>