Fix integer/float remainder with infinity argument of opposite sign

[jeremyevans]

Previously, the result was incorrect:

4.2.divmod(-Float::INFINITY)
Before: => [-1, -Infinity]
After: => [0, 4.2]

4.2.modulo(-Float::INFINITY) # or %
Before: => -Infinity
After: => 4.2

4.2.remainder(-Float::INFINITY)
Before: => NaN
After: => Infinity

Fixes [Bug #6120]

[marcandre]

I'm always confused with modulo and negative numbers 😅

Given that:

4.2.divmod(-10000)
=> [-1, -9995.8]`
4.2.modulo(-10000)
=> -9995.8
4.2.remainder(-10000)
=> 4.2

I think that divmod and modulo are ok as is, and

4.2.remainder(-Float::INFINITY)
Before: => NaN
After: => 4.2

[jeremyevans]

Obviously I get confused with them as well. New commit pushed that only affects remainder and returns the receiver if the argument is infinite.

[marcandre]

LGTM 👍