DTLS bindings (#3309)

* add DTLSv1_2 methods

* add binding to DTLSv1_get_timeout() and DTLSv1_handle_timeout()

* fix: PEP8 failed

fix the following error:

./src/_cffi_src/openssl/ssl.py:728:80: E501 line too long (80 > 79 characters)

see https://jenkins.cryptography.io/job/cryptography-pr-pep8/1954/

* Revert "add DTLSv1_2 methods"

This reverts commit e4a9150b12ddb4790159a5835f1d1136cb1b996e.

* replace 'long int' by 'long'

To be more consistent with the naming convention

cf https://github.com/pyca/cryptography/pull/3286/files/8dde92aad5db97fa176bf164783bdf9ba242edf4#r90153970

* wrap with braces

cf https://github.com/pyca/cryptography/pull/3286/files/8dde92aad5db97fa176bf164783bdf9ba242edf4#r90154057

* conditionally bind all DTLS

* rebase error

* rename wrapped function
2 files changed