OpenSSL has deprecated the function RAND_pseudo_bytes used by
crypto:rand_bytes/1, so this function is now deprecated in OTP too.

rand_bytes/3 also used this function, but was not documented
so we can remove it right away.

This commit also removes the fallback in generate_key to use
rand_bytes/1 if strong_rand_bytes/1 throws low entropy.
This is a potential incompatibility but we think it is desirable
as crypto should provide cryptographically secure functions.

This commit enables AES-GCM encryption/decryption to change its tag
length between 1 to 16 bytes.

and deprecate aes_cbc128 and aes_cbc256 in favor of aes_cbc.

This commit is pr 832 squashed, rebased and made work on master

https://github.com/erlang/otp/pull/832/commits

Using the generic EVP_* API makes it possible to unify
algorithm-specific nif functions to a single generic
function. Effectively the same change that took place on the Erlang
API in R16B01 is now applied to the C code.

The old implementation using the low-level API is kept
for compiling against old OpenSSL,
as parts of the EVP API were introduced in OpenSSL 1.0.0.

There are various minor improvements as well:
- supported algorithms are now provided by the nif code (not a mix of
  the C and Erlang code)
- remove unnecessary variables and macro definitions

Most of the changes in this commit comes from Dániel Szoboszlay
https://github.com/dszoboszlay/otp/commit/07f7056f955b324df4ace
which is part of his 'fips' branch.

Now also rebased on master branch.

by removing the spec. It's an internal function.

* andreaTP/added-aes-ecb-to-crypto/OTP-12403:
  aligned implementation following last specs
  finally fixed docs
  fixed incorrect tag
  proposal of documentation
  fixes and tests
  add aes ecb to crypto library