Update lang/erlang* to 20.2.

Some highlights:

crypto, ssl:
- The crypto API is extended to use private/public keys
  stored in an Engine for sign/verify or encrypt/decrypt
  operations.
- The ssl application provides an API to use this new
  engine concept in TLS.

ssh:
- SSH can now fetch the host key from the private keys
  stored in an Engine. See the crypto application for
  details about Engines.

ssl:
- A new command line option -ssl_dist_optfile has been
  added to facilitate specifying the many options needed
  when using SSL as the distribution protocol.

stdlib:
- Improve performance of the new string functionality
  when handling ASCII characters.

Full release notes:

  http://www.erlang.org/download/otp_src_20.2.readme

(fhajny)