RFR: 8326716: JVMTI spec: clarify what nullptr means for C/C++ developers [v4]

[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 incrementally with one additional commit since the last revision:

  review: more null pointer corrections

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19257/files
  - new: https://git.openjdk.org/jdk/pull/19257/files/4e1c48a1..48ba8f5d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19257&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19257&range=02-03

  Stats: 50 lines in 1 file changed: 0 ins; 0 del; 50 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