All set maps initialise objects as expected so dObject has the correct ID already, no need to iterate over all active objects. Also by returning a pointer we can use this function to test if an object exists at the target position.
While on msvc int8_t is typedefed to signed char we might as well match the expected data type for the dObject array
Due to the way this function is used it was easiest to also change ObjIndex to return a reference to the object instead of the index. Also added an explicit conversion from Size to Displacement to make one of the uses slightly cleaner to express.
Also updated declaration of temporary/local variables to match
convention. This includes inlining int oi in LoadMapObjects as this
matches the way SetOBjMapRange is called in other areas.