reverted regression in 3DS transformation (issue #3802)

The regression was introduced to align 3DS export and import, but in fact it broke the transformation matrices on import. This commit reverts the relevant lines. Furthermore, matrix layout was double-checked with two other 3DS importers. Export was not considered.

code/AssetLib/3DS/3DSLoader.cpp

@@ -981,9 +981,9 @@ void Discreet3DSImporter::ParseMeshChunk() {
         mMesh.mMat.a3 = stream->GetF4();
         mMesh.mMat.b3 = stream->GetF4();
         mMesh.mMat.c3 = stream->GetF4();
-        mMesh.mMat.d1 = stream->GetF4();
-        mMesh.mMat.d2 = stream->GetF4();
-        mMesh.mMat.d3 = stream->GetF4();
+        mMesh.mMat.a4 = stream->GetF4();
+        mMesh.mMat.b4 = stream->GetF4();
+        mMesh.mMat.c4 = stream->GetF4();
     } break;
 
     case Discreet3DS::CHUNK_MAPLIST: {