Add a framework for new buffer interface unit testing
Add a new extension type pygame.newbuffer.BufferMixin which allows a Python new-style class to export a new buffer interface. This enables the creation of any kind of test array, even broken, in Python. In conjunction with the ctypes module, it extends testing to multidimensional arrays, without requiring a third party package such as NumPy.
As an example case, array.array is replaced with a BufferMixin subtype in bufferproxy_test.py. This was necessary since array.array does not support the new buffer protocol in Python 2.6. or 2.7.