PyOpenGL之glVertexAttribPointer

1. PyOpenGL 開發參考文檔：
   1. LearnOpenGL-cn
   2. 簡書-Python之OpenGL筆記，大龍10
   3. PyOpenGL-API
2. glVertexAttribPointer的API

Set an attribute pointer for a given shader (index)

    index -- the index of the generic vertex to bind, see
        glGetAttribLocation for retrieval of the value,
        note that index is a global variable, not per-shader
    size -- number of basic elements per record, 1,2,3, or 4
    type -- enum constant for data-type
    normalized -- whether to perform int to float
        normalization on integer-type values
    stride -- stride in machine units (bytes) between
        consecutive records, normally used to create
        "interleaved" arrays
    pointer -- data-pointer which provides the data-values,
        normally a vertex-buffer-object or offset into the
        same.

    This implementation stores a copy of the data-pointer
    in the contextdata structure in order to prevent null-
    reference errors in the renderer.

4. 最後一個參數Pointer的坑
   在python中，不能直接設置爲0，必須要轉爲c_types的的格式，否則是跑不通的！
   此處參考了資料中代碼的寫法。