Arm neon port

[phlash]

Hi ExtIO_sddc maintainers, I had an interest in running this on Linux / ARM (RaspberryPi, OrangePi, etc.) as a downsampling head-end, so have made the necessary adjustments to the build and added a Neon-optimised R2IQ implementation.

There are also a few changes to the (out-of-date / incompatible) unittest/core_test.cpp file, as I based my work on v1.2.0 tagged build (I found that current version fails to pass unit tests on x86, crashing with a pointer problem, hence starting with last stable). Not sure what you would like to do here, please let me know?

[ik1xpv]

Hi Phlash, thank you. I appreciate your input. My programming skills are limited and I have no experience with Linux and Arm. Howard's, Hayati's, Franco's ideas and coding made it possible to get here.
My activity is reduced in Summer, when I am a full time grandfather :-)

[phlash]

Congratulations on grandfather-hood, always a priority 😄

I'm happy to wait for @howard0su, @hayguen or @fventuri to respond, while I continue into real hardware and testing!

[howard0su]

Looks good to me except wisdom files. Not sure if we want to commit into repo. My understanding is that the files are changed for different hardware.

[phlash]

Looks good to me except wisdom files. Not sure if we want to commit into repo. My understanding is that the files are changed for different hardware.

Thanks, this is true, I was simply saving them as it takes several minutes to generate on my wee ARM board. I'll pop a pattern in .gitignore and remove these from the PR.

[howard0su]

Can you resolve the conflict of unittest? then we can merge.

[phlash]

Can you resolve the conflict of unittest? then we can merge.

This should be good to merge now, although I am still unable to run unittest due to the segfault somewhere in R2IQ_impl I mentioned at the start. Would you like me to raise a new issue for that?