Net_SFTP_Stream: Use default SFTP port, if not set otherwise.
Merge pull request #119 from VaclavSir/sftp_default_port

Net_SFTP_Stream: Use default SFTP port, if no port specified
SFTP: remove isset() from constructor
AES: use ()'s for require_once

All other require_once's use them so for consistency this one ought to too
Merge branch 'master' of https://github.com/phpseclib/phpseclib