Fixes moc generation errors with boost >= 1.57

See 47fceb5f4f6019d36ea02a2eb5cd692e14327fa4 and
00983d95999697da4213c1f97c34011cdd4173f8 for comparable changes...
Merge pull request #826 from v4hn/indigo-boost-1.57

Fixes moc generation errors with boost >= 1.57