Compute the standard-normal quantile for a probability using Wichura's (1988) Algorithm
AS 241 (the PPND16 routine), the same algorithm underlying
stats::qnorm().
Details
The tail branch, which about 15% of uniform draws reach, calls log(). Where R and 'Python'
do not share a maths library, the two can therefore return different doubles for the same p.
On Windows, 14 of 1,000,000 draws differed, by 1 to 3 units in the last place.