mtab translator (v4)

[Justus Winter]

Hi folks :)

this is the fourth version of my mtab patch series. I consider it
feature complete. Notable changes:

* Deadname notifications for translators now work on libnetfs.
* The path in peropen structs is updated if a node is moved.
* Lot's of cleanups, comments, updated copyright years...
* The mtab translator drops privileges if started as translator.
* The mtab translator only follows translators bound to nodes owned by
  root or the user running the translator by default unless --insecure
  is given. This makes more sense than trying to figure out with wich
  privileges a translator has (which I believe is not trivial and in
  fact not very interesting), the root user is trusted not to bind
  malicious translator to nodes only he can bind translators to.

Now is the time to polish the RPCs and the interface. Please pay close
attention to identifier names and the way data is passed across.

For your convenience, I've pushed the branch to darnassus:

http://darnassus.sceen.net/gitweb/?p=teythoon/hurd.git;a=shortlog;h=refs/heads/feature-mtab-translator-v4

[PATCH 01/16] libnetfs: implement file_get_translator_cntl
[PATCH 02/16] libnetfs: handle dead-name notifications

Those two patches add missing functionality to libnetfs. They are
independent of the other patches and I ask for their inclusion
independently of the remaining patches.

Justus