Replace IO::Socket::SSL dependency by the lower level Net::SSLeay.

Replace IO::Socket::SSL dependency by the lower level Net::SSLeay.

Also,

  * Rename the 'SSL_verify_trusted_peer', 'SSL_ca_path', and
    'SSL_cipher_list' options to 'SSL_CApath', 'SSL_verify' and
    'SSL_cipherlist', respectively.
  * Add an option 'SSL_CAfile' to specify a file containing trusted
    certificates to use during server certificate authentication.
  * Replace Compress::Zlib dependency by the lower level
    Compress::Raw::Zlib.