feat: add math/base/special/cosf

[anandkaranubc]

Progresses #649

Description

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This pull request:

• Adds the complete implementation for math/base/special/cosf

Related Issues

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This pull request:

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

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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/cosf	$\color{green}285/285$ $\color{green}+100.00\%$	$\color{green}25/25$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}285/285$ $\color{green}+100.00\%$

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

[Planeshifter]

This applies here and elsewhere: For the benchmarks in the statistical distribution packages, we defined a function

/**
* Generates a random number on the interval [min,max).
*
* @param min    minimum value (inclusive)
* @param max    maximum value (exclusive)
* @return       random number
*/
static double random_uniform( const double min, const double max ) {
	double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
	return min + ( v*(max-min) );
}

to directly draw from the desires uniform distribution instead of inline calculations such as this. It would be good to do the same in this package's C benchmark files (and sinf and others).

[anandkaranubc]

Done!