Fix integer overflow in layer_resize in map_engine.c (#268)

* Fix integer overflow in layer_resize in map_engine.c

There's a buffer overflow bug in the function layer_resize. It allocates
a buffer `tilemap` with size `x_size * y_size * sizeof(struct map_tile)`.
But it didn't check for integer overflow, so if x_size and y_size are
very large, it's possible that the buffer size is smaller than needed,
causing a buffer overflow later.

PoC: `SetLayerSize(0, 0x7FFFFFFF, 0x7FFFFFFF);`

* move malloc to a separate line
person_get_xyz(const person_t* person, double* out_x, double* out_y, int* out_layer, bool normalize)
{
	*out_x = person->x;
	*out_y = person->y;
	*out_layer = person->layer;
	if (normalize)
		map_normalize_xy(out_x, out_y, *out_layer);
}

person_get_xyz(const person_t* person, double* out_x, double* out_y, int* out_layer, bool normalize)
{
	*out_x = person->x;
	*out_y = person->y;
	*out_layer = person->layer;
	if (normalize)
		map_normalize_xy(out_x, out_y, *out_layer);
}
