2.) change upload directory from public to private

2.) "The variable $account_settings_email_attachment_attach_id is empty on first visit"  adding isset check

2.) Minimize hook_help code as suggested by stBorchert

2.) Convert Line Delimiters to UNIX format

2.) Implements hook permission

2.) account_settings_email_attachment_enable() hold old value if exsists.
3.)account_settings_email_attachment_form_alter() change to hook_form_FORM_ID_alter()
4.)place holder used to replace t() var value

2.) Use drupal's function for file validation