Basemap creation fails for map covering pole

还没有人认领这个 Issue。

``` python
>>> Basemap(width=1000000, height=1000000, projection='stere', lat_0=-88, lon_0=-3)

Traceback (most recent call last):
File "", line 1, in
File "..\site-packages\mpl_toolkits\basemap\__init__.py", line 1085, in __init__
self._readboundarydata('gshhs',as_polygons=True)
File "..\site-packages\mpl_toolkits\basemap\__init__.py", line 1428, in _readboundarydata
if not poly.is_valid(): poly=poly.fix()
File "_geoslib.pyx", line 234, in _geoslib.BaseGeometry.fix (src/_geoslib.c:2233)
File "_geoslib.pyx", line 334, in _geoslib.Polygon.__init__ (src/_geoslib.c:3479)
IndexError: index -1 is out of bounds for axis 0 with size 0
```

Strange thing is that e.g. using `lon_0=-2` works.

I'm using basemap 1.0.8.

复现使用 projection='stere'、lat_0=-88 和 lon_0=-3 的确切 Basemap 调用，然后将其与正常工作的 lon_0=-2 情况进行比较。从 mpl_toolkits/basemap/__init__.py 中的 _readboundarydata 开始，跟踪该失败直到 _geoslib.pyx 中的 BaseGeometry.fix。完成标准是覆盖极点的地图不再引发 IndexError。

由索引模型根据 Issue 内容生成。