Layer1D autol > 1 doesn't properly rescale ymin

[mrecachinas]

Describe the bug Layer1D autol > 1 doesn't properly rescale ymin

[mrecachinas]

Need a test like the following, except with cmode: 6 and an initial buffer of 0s followed by values ranging from [very close to 0, whatever).

interactiveTest('complex scrolling line', 'Do you see a scrolling random data (0 to 1) plot that auto-scales', function(assert) {
    var container = document.getElementById('plot');
    var plot = new sigplot.Plot(container, {});
    assert.notEqual(plot, null);
    plot.change_settings({
        cmode: 3,
        autol: 5
    });
    var lyr0 = plot.overlay_pipe({
        type: 1000,
        format: "CF"
    }, {
        framesize: 32768,
        drawmode: "scrolling"
    });
    ifixture.interval = window.setInterval(function() {
        var random = [];
        for (var i = 0; i < 100; i += 1) {
            random.push(Math.random());
        }
        plot.push(lyr0, random);
    }, 100);
});