openssl support

[mchalain]

Hello,
Here my support for openssl into libcotp. I need it to embed only one hmac library on my system.
Best regards,
Marc.

This pullrequest contains:

• a wrapper around all hmac function
• a wrapper for libgcrypt
• a wrapper for libcrypto (openssl 3.0.0)
  Modifications:
• the hmac context is a dynamic pointer.
• this same pointer creation move into a function call up and free at the same level.
• the dlen getter function needs the context pointer.
• the MD5 macro is defined into the test file.
  API modifications
• none
  Testing:
• all tests from test_cotp pass for gcrypt and openssl.

[paolostivanin]

Hello,
thanks a lot for your work! I'll review it in a few days :)

[paolostivanin]

@mchalain could you please rebase and make a single commit? Also, could you please sign the commit too? thanks!

[paolostivanin]

@mchalain ping

[mchalain]

Ok to rebase. I will try to sign.

[paolostivanin]

I took care of that stuff with #56 , thanks a lot for your work, really appreciated!