RFR: JDK-8300243: Replace NULL with nullptr in share/compiler/ [v3]

[Johan Sjölen]

> Do the conversion in the share/compiler/ sub-directory and all of its files.

Johan Sjölen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge remote-tracking branch 'origin/master' into JDK-8300243
 - Fix alignment issues
 - Manual fixes
 -  Replace NULL with nullptr in share/compiler/

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Changes: https://git.openjdk.org/jdk/pull/12032/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12032&range=02
  Stats: 594 lines in 27 files changed: 0 ins; 0 del; 594 mod
  Patch: https://git.openjdk.org/jdk/pull/12032.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12032/head:pull/12032

PR: https://git.openjdk.org/jdk/pull/12032