Replaced PyErr_NoMemory with ImagingError_MemoryError

[radarhere]

In several locations,

• Replaced PyErr_NoMemory with ImagingError_MemoryError
  

  Pillow/src/_imaging.c

  Lines 279 to 283 in c1707d5

  	void *
  	ImagingError_MemoryError(void)
  	{
  	return PyErr_NoMemory();
  	}

• Simplified

ImagingError_MemoryError();
return NULL;

into

return ImagingError_MemoryError();