The linux/input-even-codes.h doesn't exist (yet) on older linux versions
The linux/input-even-codes.h used to be part of the linux/input.h and now days it's a separate file #included from linux/input.h
As the test includes linux/input.h anyway there's no need to separately include linux/input-even-codes.h and doing away with it makes the code backwards compatible with older kernels.