Extended Session.display_variables().

Method now hides next redraw when called in user input getter.

Example:

    Red Example Score (2013) - materials

        1: magic numbers (Red Example Score)
        2: pitch range inventory (Red Example Score)
        3: tempo inventory (Red Example Score)

        material - new by hand (nmh)
        material - new for editable mainline class (nmc)

    > nmh

    Package name> sdv
    command_history: ['ssx', 'red', 'm', 'nmh', 'sdv']
    controller_stack:
        ScoreManager()
        ScorePackageManager('/Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score')
        MaterialPackageWrangler()
        <UserInputGetter (1)>
    current_score_package_manager: ScorePackageManager('/Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score')
    hide_hidden_commands: True
    hide_next_redraw: False
    is_autoadding: False
    is_in_confirmation_environment: True
    is_in_editor: False
    is_in_user_input_getter: True
    last_asset_path: '/Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score'
    scores_to_display: 'example'

    Press return to continue.

    Package name> q