Fix T38030.
In c++ source we use one list for triangles and an other for quads, but KX_PolyProxy doesn't care about that and return the vertex offset in its list. So we just have to compute the offset of each RAS_DisplayArray to its previous to have an absolute vertex index.
Reviewers: moguri, campbellbarton, kupoman, agoose77, brita_, hg1
Reviewed By: agoose77, hg1
Projects: #game_engine
Maniphest Tasks: T38030
Differential Revision: https://developer.blender.org/D1324
2a305580b2