clarify more details on section "2.1 More non-blocking"

2.1 More non-blocking

 Make sure we don't ever loop because of non-blocking sockets returning

 EWOULDBLOCK or similar. The GnuTLS connection etc.

 EWOULDBLOCK or similar. Blocking cases include:

 - Name resolves on non-windows unless c-ares is used

 - GnuTLS SSL connections

 - NSS SSL connections

 - Active FTP connections

 - HTTP proxy CONNECT operations

 - SOCKS proxy handshakes

 - file:// transfers

 - TELNET transfers

 - The "DONE" operation (post transfer protocol-specific actions) for the

   protocols SFTP, SMTP, FTP. Fixing Curl_done() for this is a worthy task.

2.2 Remove easy interface internally