Saving resampled data to `out` pointer instead of returning a copy

[eshaz]

I'm working on a program that is using SharedMemory to send data between processes and it would be really nice if I could have samplerate just write directly to the buffer, so I don't have to copy it from the return result.

Thinking all that would be needed is to add an optional out parameter that, if present, is used instead of the below code.

python-samplerate/src/samplerate.cpp

Lines 164 to 168 in d737def

	// allocate output array
	std::vector<size_t> out_shape{new_size};
	if (inbuf.ndim == 2) out_shape.push_back(static_cast<size_t>(channels));
	auto output = py::array_t<float, py::array::c_style>(out_shape);
	py::buffer_info outbuf = output.request();

Looks like libsamplerate already supports setting the out pointer:

typedef struct
      {   float  *data_in, *data_out ;

          long   input_frames, output_frames ;
          long   input_frames_used, output_frames_gen ;

          int    end_of_input ;

          double src_ratio ;
      } SRC_DATA ;