Log Message:
Update to 0.13.1, based on patches from recht@ via tech-pkg.

Additionally, fix it to compile against openssl-0.9.7i, the
current pkgsrc version; due to its way of checking compatibility,
py-m2crypto is extremely picky about constness.
If this works with other versions too, just add them to the pattern.

 Changes since 0.12/0.11
-------------------------
- Patches from Artur Frysiak. Thanks Artur.
  = Allow using a passphrase callback in class SMIME.
  = Added method get0_signers to class PKCS7, which retrieves signers'
    certificates from a PKCS7 blob.
  = Added methods as_pem and save_pem to class X509.
  = Added file version.py.
  = Allow SSL.Context.load_verify_locations to accept both 'cafile' and
    'capath'.
- Fixed BIO.read() not reading until EOF. Thanks to Egil Muller
  for suggestion.
- Honour 'mode' parameter in SSL.Connection.makefile. Thanks again to Egil
  Muller.
- Roger Binns contributed epydoc-generated docs for M2Crypto. Thanks Roger.
- Peter Teniz contributed patches to create X.509 requests and certificates.
  Thanks Peter.
- Updated Medusa to 0.54.
- Make various OpenSSL bignum functions (written long ago) available to Python.