feat: add C implementation for math/base/special/round2

[gunjjoshi]

Description

What is the purpose of this pull request?

This pull request:

• adds C implementation for math/base/special/round2.

double stdlib_base_round2( const double x );

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves a part of [RFC]: Add C implementations to base special math functions (tracking issue) #649.

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

• I was getting errors such as conflict in already defined variables in header files for HUGE. Also, there was a problem in calculating the value of the constants at compile time. That's why, I have made changes in the variable name, and have calculated it inside the function.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

---

@stdlib-js/reviewers

[kgryte]

Renaming HUGE was the right thing to do, so no issues there.

[Planeshifter]

Looks all good; let's get it in!