readshapefile fails on certain filenames

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Hi,

(Tested with basemap 1.0.6)

This works:

`m.readshapefile('foo.shp', 'my_shape')`

while this fails:

`m.readshapefile('bar_0.1.shp', 'my_shape')`

```
raise IOError('error reading shapefile %s.shp' % shapefile)
fields = shf.fields
coords = []; attributes = []

IOError: error reading shapefile bar_0.1.shp
```

Note that foo.shp and bar_0.1.shp are exactly the same file except for the filename. So it seems that the additional `.` causes the problem. Minimal example to reproduce behavior:

Rename `huralll020.{shp,dfb,shx}` to `huralll020_0.1.{shp,dbf,shx}` and change filename in `examples/hurrtracks.py` accordingly. Run hurrtracks.py.

Of course the obvious workaround is not to use `.` in filenames. But this is somewhat impracticable as I have a large number or files and would like keeping the filenames consistent accross filetypes (netCDF, shapfiles, pngs, etc).

Is there an easy fix?

Thanks very much,

Andy

Start with the readshapefile entry point and the reproduction in examples/hurrtracks.py. Rename the huralll020 shapefile components as described, run hurrtracks.py, and trace why the dotted filename fails. Done means the same shapefile can be read with a filename such as huralll020_0.1 while the existing example still works.

Written by the indexing model from the issue text.