Simplify requirement of skipif.inc files

[carusogabriel]

AFAIK, the skipif.inc always lived in the same directory, and IMHO we don't need these complex statements to require it. A simple require 'skipif.inc' resolves, right?

Also, I've unified to require, as (if I'm not wrong) is safer than include and faster than require_once and include_once 😄

[krakjoe]

I'm not sure about this, it's technically true that once variants are slower, but in this case whatever function is used is just causing the interpreter to exit, and the difference won't amount to anything meaningful.

I'm also not sure that future test writers will care about the conventions you are trying to establish.

[carusogabriel]

I'm also not sure that future test writers will care about the conventions you are trying to establish.

@krakjoe I can compromise myself to review new tests, but also, we can do this by updating our Quality Assurance. What do you think?

[carusogabriel]

Closing as we shouldn't standardize such thing