Basemap creation fails for map covering pole

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``` 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.

Reproduce the exact Basemap call with projection='stere', lat_0=-88, and lon_0=-3, then compare it with the working lon_0=-2 case. Start in mpl_toolkits/basemap/__init__.py at _readboundarydata and follow the failure into _geoslib.pyx at BaseGeometry.fix. Done means the pole-covering map no longer raises the IndexError.

Written by the indexing model from the issue text.