Add the function st_makepolygon to create a polygon

Create a polygon formed by a outlinestring and a set of holes.

```mysql
SELECT ST_MakePolygon('LINESTRING (100 250, 100 350, 200 350, 200 250, 100 250)'::GEOMETRY, 
'LINESTRING(120 320, 150 320, 150 300, 120 300, 120 320)'::GEOMETRY );
```

Input linestrings must be closed.