std.internal.math.summation added

std.internal.math.summation: tabs

std.algorithm: sum (Kahan and Pairswise) update

*.mak update

std.interanl.math.summation update

std.numeric: added fsum

std.interanl.math.summation update

std.interanl.math.summation update

std.interanl.math.summation update

std.interanl.math.summation add local fabs

std.interanl.math.summation

Docs update

minor update