RFR: JDK-8273056 java.util.random does not correctly sample exponential or Gaussian distributions [v2]

[Jim Laskey]

> The modified ziggurat algorithm is not correctly implemented in `java.base/jdk/internal/util/random/RandomSupport.java`. 
> 
> Create a histogram of a million samples using 2000 uniform bins with the following range: 
> Exponential range from 0 to 12. Gaussian range from -8 to 8. 
> 
> This does not pass a Chi-square test. If you look at the histogram it is obviously not showing the shape of the PDF for these distributions. Look closely at the range around zero (e.g. +/- 0.5).

Jim Laskey has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into 8273056
 - 8273056 - java.util.random does not correctly sample exponential or Gaussian distributions

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6353/files
  - new: https://git.openjdk.java.net/jdk/pull/6353/files/b10c4793..b6679479

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6353&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6353&range=00-01

  Stats: 69228 lines in 1218 files changed: 46725 ins; 12712 del; 9791 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6353.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6353/head:pull/6353

PR: https://git.openjdk.java.net/jdk/pull/6353