This seems to satisfy g++ 4.4.2, which otherwise complains like this:
In file included from ../src/proc/mobject/session/session-impl.hpp:53,
from ../src/proc/mobject/session/sess-manager-impl.hpp:28,
from ../src/proc/mobject/session/sess-manager-impl.cpp:41:
../src/proc/mobject/session/placement-index.hpp:163: error:
declaration of ‘typedef class mobject::Placement<mobject::MObject,
mobject::MObject> mobject::session::PlacementIndex::PlacementMO’
../src/proc/mobject/placement.hpp:244: error: changes meaning of
‘PlacementMO’ from ‘typedef class mobject::Placement<mobject::MObject,
mobject::MObject> mobject::PlacementMO’
217d17107d