RFR: JDK-8300243: Replace NULL with nullptr in share/compiler/ [v2]

[Johan Sjölen]

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

Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:

  Fix alignment issues

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12032/files
  - new: https://git.openjdk.org/jdk/pull/12032/files/b23cb6ca..4ad6dc3a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12032&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12032&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 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