Refactored Net_SSH2::$identifier and added unit tests

Added return tag
Fixed typo
Rewritten test to just check for possible combinations
Replaced else { if ()...} with elseif() {}
Fixed cs
Fixed missing dataProvider in test
Merge branch 'master' into php5
Fixed typos
SSH2: add new line in docblock comment
Merge branch 'ssh2-identifier' into php5
Merge branch 'php5' of https://github.com/phpseclib/phpseclib into php5