config/cpu cleanup

[jcowgill]

Fixes #56

It turns out all the cycles.h files are also unused, so I've removed those as well. The atomicity.h files could also be replaced with the generic implementation but I wasn't sure if that was kept for a reason (other platforms?)

[jdek]

Did you test the other platforms? (Do they still work?)

[jcowgill]

No, I haven't. I simply removed the files based on them never being included anywhere else in the jack codebase. In theory this PR has absolutely no effect on any platform.

[adiknoth]

LGTM, this stuff is really unused.

[adiknoth]

@jcowgill I think we should replace the atomicity.h files with the generic one - pretty much everyone should be using the compiler builtins by now.

If you want to send another PR, I'm happy to merge.

Thanks

[jcowgill]

@adiknoth OK I can send another PR. Does jack have a minimum GCC version? I ask because the __sync functions are deprecated and should be replaced if possible. For GCC, __sync* requires 4.1, __atomic* requires 4.7, and C11's stdatomic.h requires 4.9.

[adiknoth]

Let's use C11 if available or 4.7 if not. GCC 4.9 was released in April 2014, that's almost three years, 4.7 in March 2012, almost five years.

According to wikipedia: "A standard macro __STDC_VERSION__ is defined with value 201112L to indicate that C11 support is available."

So we can have something like

#if __STDC_VERSION__ >= 201112L #include <stdatomic.h> ... #else ... #fi

Thanks!