Update SSH2.php

Use of undefined property: "$this->bitmask".

In context, it seems that it should reference the "bitmap" property.
Merge pull request #167 from phonzie/patch-2

SSH2.php: Use of undefined property: "$this->bitmask"
SFTP_Stream: Fixed typo in _parse_path

typo: isset($this->contenxt)
should be $this->context
Merge pull request #168 from phonzie/patch-3

SFTP_Stream: Fixed typo in _parse_path

* phonzie/patch-3:
  SFTP_Stream: Fixed typo in _parse_path
Initing eof to false

The call _stream_eof() must return a boolean, not null.
Returning null makes PHP believe that the method wasn't implemented.

Fixes #170
Making Net_SFTP::chdir capable of handling the empty string.

Fixing a ugly notice when using the empty string as parameter for chdir:
  Notice: Uninitialized string offset: -1 in Net/SFTP.php line 617
Making Net_SFTP::chdir capable of handling the empty string.

Updated patch after hint from bantu.
Merge pull request #172 from PVince81/sftp-stream-feof-fix

Initing eof to false
SFTP/Stream: log when constructor is called
Merge pull request #173 from h4cc/patch-1

Making Net_SFTP::chdir capable of handling the empty string.
SFTP: don't do $dir[-1] check if $dir === ''