Check_MK Werk 5465: Fixed calculation of standard deviation.

ID: 5465 Title: Fixed calculation of standard deviation. Component: Livestatus Level: 1 Class: Bug fix Version: 1.5.0i2 Note: This fixes only a slightly esoteric feature, namely "Stats: std ..." headers. Normal users are not affected, only those using this header via self-written scripts. Livestatus incorrectly used a bias correction when calculating the standard deviation. For more mathematical background see: https://en.wikipedia.org/wiki/Bessel%27s_correction http://mathworld.wolfram.com/StandardDeviation.html