Crypto library code refactoring

There's a couple of issues or MRs that are related to crypto code refactoring:

• Unification of random routines #221 (closed)
• Refactoring HMAC routines #175 (closed) !155 (closed)
• Remove OpenSSL 0.9.x support and add LibreSSL >= 2.7.0 support #191 (closed) !175 (merged)
• Remove compilation without DNSSEC #24 (closed)
• Always use OpenSSL or PKCS#11 random data providers #165 (closed)
• Replace DISABLE_MD5 with proper return code checking in crypto provider calls
• Review the public key cryptography code and cross-checking with draft-ietf-dnsop-algorithm-update
• Refactor message digest functions (similar to #175 (closed))
• Change ECDSA to Deterministic Usage Elliptic Curve Digital Signature Algorithm (RFC 6979) #299
• Update documentation, release notes and CHANGES #426 (closed)