[moses-smt/mosesdecoder] ab1e10: Compiler error for boost < 1.42

[GitHub <no...@gi...>]

  Branch: refs/heads/master
  Home:   https://github.com/moses-smt/mosesdecoder
  Commit: ab1e10c555111ff8aa4e948588ce86cff3c93a88
      https://github.com/moses-smt/mosesdecoder/commit/ab1e10c555111ff8aa4e948588ce86cff3c93a88
  Author: Kenneth Heafield <gi...@kh...>
  Date:   2012-11-16 (Fri, 16 Nov 2012)

  Changed paths:
    M search/vertex_generator.hh

  Log Message:
  -----------
  Compiler error for boost < 1.42