`logabssinh`

[Andrés Riedemann]

LogExpFunctions already has logcosh. normally, when those terms appear, there is also log(abs(sinh)) terms. In my specific field, that term appear in natural-gas properties:

logsinh can be expressed in terms of LogExpFunctions.log1mexp:

function logabssinh(x::Real)
    abs_x = abs(x)
    return abs_x + log1mexp(- 2 * abs_x) - IrrationalConstants.logtwo
end

Is it ok to have this function here?