RFR: 8301244: Tidy up compiler specific warnings files [v9]

[Julian Waters]

> Cleans up some code in compilerWarnings_*.hpp files to be slightly neater

Julian Waters has updated the pull request incrementally with four additional commits since the last revision:

 - compilerWarnings_visCPP.hpp
 - Spelling
 - compilerWarnings_gcc.hpp
 - macros.hpp

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12255/files
  - new: https://git.openjdk.org/jdk/pull/12255/files/8ba0ff35..30561ee1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12255&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12255&range=07-08

  Stats: 9 lines in 3 files changed: 0 ins; 3 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/12255.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12255/head:pull/12255

PR: https://git.openjdk.org/jdk/pull/12255