SSH2: connect to server in login() function

this change will make it so some parameters can be set after the
Net_SSH2 object has been created. eg. instead of doing
define('NET_SSH2_LOGGING', NET_SSH2_LOG_COMPLEX) one can now do
$ssh->setLogging(...) or something.
SSH2: add phpdoc header
SSH2: timeout set in constructor != timeout set by setTimeout()
SSH2: syntax error
SSH2: phpdoc changes
SSH2: != -> |=
SSH1: do fsockopen() call when login has been called
SSH: clarify role of constructor / connection timeout

Also, in Net_SSH2::_connect() $host is used in multiple places. Rather than changing all references to {$this->host}:{$this->port} preserve existing $host reference and update it accordingly
SSH2: phpdoc updates
SSH2: move _connect() call to _login() from login()

Per bantu, this is required for it to work with Net/SFTP.php
Merge pull request #308 from terrafrost/ssh2-connect-after-login

SSH2: connect to server in login() function

* terrafrost/ssh2-connect-after-login:
  SSH2: move _connect() call to _login() from login()
  SSH2: phpdoc updates
  SSH: clarify role of constructor / connection timeout
  SSH1: do fsockopen() call when login has been called
  SSH2: != -> |=
  SSH2: phpdoc changes
  SSH2: syntax error
  SSH2: timeout set in constructor != timeout set by setTimeout()
  SSH2: add phpdoc header
  SSH2: connect to server in login() function