feat: add math/base/special/log1pf

[gunjjoshi]

Progresses #649.

Description

What is the purpose of this pull request?

This pull request:

• adds math/base/special/log1pf, which would be the single-precision equivalent for math/base/special/log1p.

float stdlib_base_log1pf( const float x )

Related Issues

Does this pull request have any related issues?

This pull request:

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

Questions

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No.

Other

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No.

Checklist

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• Read, understood, and followed the contributing guidelines.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/log1pf	$\color{red}358/370$ $\color{green}+96.76\%$	$\color{red}31/35$ $\color{green}+88.57\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{red}358/370$ $\color{green}+96.76\%$

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

[gunjjoshi]

Suggested change

	tol = 1.0e07 * EPS * absf( e );
	tol = 1.0e07 * EPS * absf( e );

@kgryte @Planeshifter The JS implementation requires a very large tolerance for numbers in the range -0.9999 to -0.41422. But, for the C implementation, the required tolerance equals EPS * absf( e ) only. I checked the implementation from the FreeBSD source, but couldn't find the reason.

FreeBSD reference: https://svnweb.freebsd.org/base/release/12.2.0/lib/msun/src/s_log1pf.c?revision=367086&view=markup