hurd: Fix more tests

  * debian/patches/hurd-i386/libpthread_version.diff: Remove now-useless part.
  * debian/patches/hurd-i386/local-hurdsig-global-dispositions-version.diff:
    Likewise.
  * debian/testsuite-xfail-debian.mk: Update.
  * debian/patches/hurd-i386/git-htl-getspecific.diff: New upstream patch to
    fix __libc_getspecific.