Blender Git Loki

Fix T48176: Shrinkwrap crashes when multiple objects uses same target

Annoying bug caused by temp nature of looptri layer for CCGDM.

Fixed in a similar to CCG loops by using lock when allocating and
filling looptri arrays.

Real fix would be to make sure this array is allocated on object
evaluation using DAG's eval_flag, but that's more involved change
which we'll work on later.