Moved global constants to class constants
Merge branch 'php5' of https://github.com/phpseclib/phpseclib into NetPackageConstantsFix

Conflicts:
	phpseclib/Net/SSH2.php
Merge pull request #532 from cnelissen/NetPackageConstantsFix

Net package constants fix

* cnelissen/NetPackageConstantsFix:
  Moved global constants to class constants