Add function Math.nearestInteger

[beutlich]

Cherry-picked from #3247 as proposed by #3247 (review).

[casella]

LGTM

[henrikt-ma]

More though seems needed on how to obtain a useable expression variability of the function result.

[henrikt-ma]

(Just restoring my Request changes after changing my mind back and forth.)

[HansOlsson]

The general idea is good, but when using it outside of functions it becomes messy.

It seems we need the annotation GenerateEvents=true and update such functions in terms of variability, e.g., along the lines of modelica/ModelicaSpecification#3610

[beutlich]

The general idea is good, but when using it outside of functions it becomes messy.

I removed the usage in block Modelica.Blocks.Math.RealToInteger. @casella @HansOlsson Please add your review again.

[HansOlsson]

LGTM.
Combined with modelica/ModelicaSpecification#3610 it will be generally useful.

One could possibly add "away from zero" already in description as the preferred method depends, https://en.wikipedia.org/wiki/Rounding (But it may also be too long.)

[beutlich]

One could possibly add "away from zero" already in description

Incorporated. Fell free to review this last change.

@henrikt-ma may I kindly ask for a second review. Thanks.

[henrikt-ma]

I don't think this can be accepted until it is relying on language features of a released version of the specification. According to current semantics, the output of this is a non-discrete-time Integer, which I'm pretty sure is not the intention.