Added trigonometric functions that work in units of half turns, rather than
radians. The new functions :func:`math.acospi`, :func:`math.asinpi`,
:func:`math.atanpi`, and :func:`math.atan2pi` return half-turn angles. The
new functions :func:`math.cospi`, :func:`math.sinpi`, and :func:`math.tanpi`
take half-turn angle arguments. These functions are recommended by IEEE
754-2019 and standardized in C23.
