[jdk11u-dev] RFR: 8215131: Pandoc 2.3/build documentation fixes

[George Adams]

changes apply cleanly except for the cross-compile markdown table which was updated in https://github.com/openjdk/jdk11u-dev/commit/90ac8aea0372a6f26592015ca42b98b109ac89f7

Prerequisite to backporting https://github.com/openjdk/jdk/commit/4f45b5f9739e5a5e7d1c4f80da9c42e0d77dd0bf

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Depends on: https://git.openjdk.org/jdk11u-dev/pull/1313

Commit messages:
 - Backport 8c00337375d67f6e7991073da8a93e2a6d733a24

Changes: https://git.openjdk.org/jdk11u-dev/pull/1314/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1314&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8215131
  Stats: 35 lines in 3 files changed: 14 ins; 1 del; 20 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1314.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1314/head:pull/1314

PR: https://git.openjdk.org/jdk11u-dev/pull/1314