* gnulib/*, config/gnulib/*: upgrade gnulib to
  3fe906e98202a591a6a14010aec1538adfd821b6.


git-svn-id: https://svn.code.sf.net/p/amanda/code/amanda/branches/3_3@5260 a8d146d6-cc15-0410-8900-af154a0219e0