RFR: Addition of a causes link type [v9]

[Roger Calnan]

> There is a proposal for the addition of a causes/caused by link type.  Tied into that there is now a separate section which covers the main link types that we use

Roger Calnan has updated the pull request incrementally with two additional commits since the last revision:

 - Update src/guide/jbs-jdk-bug-system.md
   
   Co-authored-by: Alexey Ivanov <alexey.ivanov at oracle.com>
 - Update src/guide/backporting.md
   
   Co-authored-by: Alexey Ivanov <alexey.ivanov at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/guide/pull/139/files
  - new: https://git.openjdk.org/guide/pull/139/files/1bb0f8b5..2cb52704

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=guide&pr=139&range=08
 - incr: https://webrevs.openjdk.org/?repo=guide&pr=139&range=07-08

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/guide/pull/139.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/139/head:pull/139

PR: https://git.openjdk.org/guide/pull/139