Recent debian hurd fixes

[Samuel Thibault <sthibault@debian.org>]

Hello,

For information, I have worked on some base packages:

- mesa
- gegl
- qtbase
- xorg-server
- more that I don't remember

which has unlocked quite a few packages.

I have also fixed an issue with the mtab translator which was
yielding invalid port errors, notably when using pbuilder. The
remap prefix translator fix from Joan is also in, as well as the
symlink-created-by-Linux fix. Damien's work on cleaning the pci-arbiter
is also in.

And I'm on adding posix_openpt, which should give vte2.91, unlocking
some more packages.

Samuel