RFR: 8282573: ByteBufferTest.java: replace endless recursion with RuntimeException in void ck(double x, double y) [v2]

[Emanuel Peter]

> There are two functions that check for equality.
> void ck(long x, long y): already throws a RuntimeException if we observe inequality
> void ck(double x, double y): called itself, leading to endless recursion and a StackOverflowError.
> 
> Instead of the recursion, I now also throw a RuntimeException.
> 
> This can currently be triggered with
> `path-to-jtreg/jtreg -va -s -jdk:jdk-path -javaoptions:"-XX:+UnlockDiagnosticVMOptions -XX:-TieredCompilation -XX:+StressGCM -XX:+OptoScheduling -XX:StressSeed=293843391" test/hotspot/jtreg/compiler/intrinsics/unsafe/HeapByteBufferTest.java `
> (see bug [JDK-8282555](https://bugs.openjdk.java.net/browse/JDK-8282555))
> 
> This way I could verify that instead of StackOverflowError we now get RuntimeException, as desired.
> Ran some basic tests to ensure I didn't break things.

Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:

  removed unnecessary conditions

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7674/files
  - new: https://git.openjdk.java.net/jdk/pull/7674/files/4eca7cf8..17ad7a21

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7674&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7674&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7674.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7674/head:pull/7674

PR: https://git.openjdk.java.net/jdk/pull/7674