fix: ensure stdlib_float16_bits_t is defined for all stdlib_float16_t type definitions

[sathwikv2005]

Resolves #13147.

Description

What is the purpose of this pull request?

This pull request:

• fixes the conditional definition of stdlib_float16_bits_t in ctor.h.
• moves the stdlib_float16_bits_t typedef outside the native _Float16 detection conditional so, that it is available on compilers with native _Float16 support, matching the documented API.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [BUG]: stdlib_float16_bits_t is conditionally undefined on compilers with native Float16 support #13147

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

Checklist

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• Read, understood, and followed the contributing guidelines.

AI Assistance

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Coverage Report

Package	Statements	Branches	Functions	Lines
number/float16/ctor	$\\color{green}331/331$ $\\color{green}+100.00\\%$	$\\color{green}13/13$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}331/331$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.