RFR: 8324286: Fix backsliding on use of nullptr instead of NULL

[Johan Sjölen]

On Mon, 22 Jan 2024 10:39:12 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this change that removes some new (since JDK-8299837) uses of
> NULL in HotSpot code.  Most of the changes are in comments, replacing "NULL"
> with either "nullptr" (for code snippets) or "null" (for textual description),
> as was done for JDK-8299837.  There are a small number of new uses of NULL in
> code, which are replaced with nullptr.
> 
> Testing: mach5 tier1

LGTM and trivial

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Marked as reviewed by jsjolen (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17516#pullrequestreview-1836182519