Ooh, those were some highly cryptic and verbose warnings indeed ;p.
Fixed it so the std flag gets automagically enforced where it's needed (GCC < 5.1), and silenced that pragma warning

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Also added a bit of hand-holding for really old kernel headers, even if that wasn't an issue in practice, because that was for button_scan, which is Kobo specific, and my crappy old kernel headers were from Kindle kernels

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