HeadingPitchRoll.fromQuaternion clamps pitch asin

[bkuster]

Issue

When evaluating a QuaternionSpline, it may sometimes happen, that the pitch value for looking straight down (-90°) is in fact larger then 1 by a rounding error of ~10^12. When using HeadingPitchRoll.fromQuaternion, this results in the .pitch value being NaN.

Fix

Instead of using Math.asin to determine the pitch, use CesiumMath.asinClamped.

[cesium-concierge]

Thanks for the pull request @bkuster!

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[hpinkos]

Good catch, thanks @bkuster!