Strange Cython error with char arrays of particular length

README

I ran into a strange cython issue where structs containing members of type char[], were failing when they
were a particular length. 

This gist contains a simple example that reproduces the issue:

```
$ python gen_pyx.py
$ python setup.py build_ext --inplace
$ python runtest.py
```

Output from `runtest.py`:

```
Failed length 19:Expected a dimension of size 19, got 9
Failed length 29:Expected a dimension of size 29, got 9
Failed length 39:Expected a dimension of size 39, got 9
Failed length 49:Expected a dimension of size 49, got 9
Failed length 59:Expected a dimension of size 59, got 9
Failed length 69:Expected a dimension of size 69, got 9
Failed length 79:Expected a dimension of size 79, got 9
Failed length 89:Expected a dimension of size 89, got 9
Failed length 99:Expected a dimension of size 99, got 9
```

gen_pyx.py

template = '''\
cdef packed struct L{L}_type:
    char[{L}] x

def test_L{L}(x):
    cdef:
        L{L}_type[:] y

    y = x
    return y[0].x

'''

if __name__ == '__main__':
    with open('chartest.pyx', 'wt') as f:
        for k in xrange(1, 100):
            f.write(template.format(L=k))

runtest.py

import numpy as np
import chartest


def test_item(L):
    test_method = getattr(chartest, 'test_L{len}'.format(len=L))

    dtype = [('x', 'S{len}'.format(len=L)),]
    x = np.recarray(10, dtype=dtype)
    x.x = b'x'

    try:
        r = test_method(x)
    except ValueError, e:
        print 'Failed length {}:'.format(L) + str(e)


if __name__ == '__main__':
    for k in xrange(1, 100):
        test_item(k)

setup.py

from distutils.core import setup
from Cython.Build import cythonize

setup(
    ext_modules = cythonize("chartest.pyx")
)