py-cryptodome: updated to 3.7.0

3.7.0:

New features
* Added support for Poly1305 MAC (with AES and ChaCha20 ciphers for key derivation).
* Added support for ChaCha20-Poly1305 AEAD cipher.
* New parameter output for Crypto.Util.strxor.strxor, Crypto.Util.strxor.strxor_c,
  encrypt and decrypt methods in symmetric ciphers (Crypto.Cipher package).
  output is a pre-allocated buffer (a bytearray or a writeable memoryview)
  where the result must be stored.
  This requires less memory for very large payloads; it is also more efficient when
  encrypting (or decrypting) several small payloads.

Resolved issues
* AES-GCM hangs when processing more than 4GB at a time on x86 with PCLMULQDQ instruction.

Breaks in compatibility
* Drop support for Python 3.3.
* Remove Crypto.Util.py3compat.unhexlify and Crypto.Util.py3compat.hexlify.
* With the old Python 2.6, use only ctypes (and not cffi) to interface to native code.

(adam)