Update to 1.9.0
    
    - New upstream release 1.9.0
      - Adds ECDSA keys and host key support when using OpenSSL
      - Adds ED25519 key and host key support when using OpenSSL 1.1.1
      - Adds OpenSSH style key file reading
      - Adds AES CTR mode support when using WinCNG
      - Adds PEM passphrase protected file support for libgcrypt and WinCNG
      - Adds SHA256 hostkey fingerprint
      - Adds libssh2_agent_get_identity_path() and libssh2_agent_set_identity_path()
      - Adds explicit zeroing of sensitive data in memory
      - Adds additional bounds checks to network buffer reads
      - Adds the ability to use the server default permissions when creating sftp directories
      - Adds support for building with OpenSSL no engine flag
      - Adds support for building with LibreSSL
      - Increased sftp packet size to 256k
      - Fixed oversized packet handling in sftp
      - Fixed building with OpenSSL 1.1
      - Fixed a possible crash if sftp stat gets an unexpected response
      - Fixed incorrect parsing of the KEX preference string value
      - Fixed conditional RSA and AES-CTR support
      - Fixed a small memory leak during the key exchange process
      - Fixed a possible memory leak of the ssh banner string
      - Fixed various small memory leaks in the backends
      - Fixed possible out of bounds read when parsing public keys from the server
      - Fixed possible out of bounds read when parsing invalid PEM files
      - No longer null terminates the scp remote exec command
      - Now handle errors when Diffie Hellman key pair generation fails
      - Fixed compiling on Windows with the flag STDCALL=ON
      - Improved building instructions
      - Improved unit tests
    - Needs OpenSSL ≥ 1.0.1 now as ECC support is assumed
    - Modernize spec somewhat as EL-6 can no longer be supported