some work on procfs

[Justus Winter]

Hi,

currently procfs doesn't allow one to alter the options at runtime
using fsys_set_options. This is necessary to make mount -oremount
work. I also noticed that fsys_get_options would only return the
translators name, but not its options, so I've implemented this as
well.

FWIW this is meant to be applied on top of procfs as found in the hurd
packaging git with the patches in debian/patches applied. Please let
me know if that is inappropriate.

Comments are welcome :)

Cheers,
Justus