Decrypts a stream of bytes from in_stream to out_stream using mode.

def decrypt_stream(mode, in_stream, out_stream, block_size = BLOCK_SIZE, padding = PADDING_DEFAULT):
    'Decrypts a stream of bytes from in_stream to out_stream using mode.'

    decrypter = Decrypter(mode, padding = padding)
    _feed_stream(decrypter, in_stream, out_stream, block_size)