X509Extension/X509ExtensionType is anachronistic - only one is required in non-ancient versions of Python

[Jean-Paul Calderone]

Ages ago, it was necessary to have a factory function for creating instances of C types separate from the C type object itself. This has long since changed, and having two different objects like this for each type (essentially all the types in pyOpenSSL suffer from this) is pointless and confusing.

The names in each pair should become synonyms for the same object. This should be the type object, and it should be possible to use the type object to instantiate the type.