RFR: 8326716: JVMTI spec: clarify what nullptr means for C/C++ developers [v6]

[Serguei Spitsyn]

> The following RFE was fixed recently:
> [8324680](https://bugs.openjdk.org/browse/JDK-8324680): Replace NULL with nullptr in JVMTI generated code
> 
> It replaced all the `NULL`'s in the generated spec with`nullptr`. JVMTI agents can be developed in C or C++.
> This update is to make it clear that `nullptr` is C programming language `null` pointer.
> 
> I think we do not need a CSR for this fix.
> 
> Testing: N/A (not needed)

Serguei Spitsyn has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:

 - Merge
 - review: consistency and stylistical corrections
 - review: more null pointer corrections
 - review: replace nullptr with null pointer in the docs
 - review: corrected the nullptr clarification
 - 8326716: JVMTI spec: clarify what nullptr means for C/C++ developers

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Changes: https://git.openjdk.org/jdk/pull/19257/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19257&range=05
  Stats: 82 lines in 4 files changed: 0 ins; 0 del; 82 mod
  Patch: https://git.openjdk.org/jdk/pull/19257.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19257/head:pull/19257

PR: https://git.openjdk.org/jdk/pull/19257