[Discuss-gnuradio] Volk in place

[Stephen Larew]

I would like to use volk functions where the input memory is also used to store 
the output. e.g. the numerator given to volk_divide is also the result of the 
division:
```
volk_32fc_magnitude_squared_32f_a(out, in0, N);
volk_32f_x2_divide_32f_a(out, out, in1, N);
```
I have not seen any official documentation indicating that in place ops are 
allowed. Of course, maybe I missed something.

A quick search brings up a few references; the most recent discussion was under 
the subject "VOLK division between complexes” where Marcus Müller suggested 
doing a `volk_32fc_magnitude_squared_32f` in place. In another discussion, 
under the subject "[VOLK] Test-case behaviour,” Martin Braun indicates that in 
place ops should work and documentation would be considered.

I’m mostly curious to know if this would be platform/instruction specific or if 
the in place ops should be guaranteed to work for any given kernel.  I’m about 
to test to see if in place ops works for my use case now.  I’ll report back.

-Stephen