--- unshift(obj1[, obj2 ...])
--- unshift([obj1[, obj2 ...]])         ruby 1.8 feature

    obj1, obj2 ... ֤Ƭޤself ֤ޤ

    push, pop, shift ⻲ȤƤ
    

    :
        arr = [1,2,3]
        arr.unshift 0
        p arr             #=> [0, 1, 2, 3]
        arr.unshift [0]
        p arr             #=> [[0], 0, 1, 2, 3]
        arr.unshift 1, 2
        p arr             #=> [1, 2, [0], 0, 1, 2, 3]

    ruby 1.8 feature: ꤷʤв⤷ޤ

