RFR: Add material about updating the CSR when a backout occurs. [v2]

[Stuart Marks]

> Also, add a small fix to the Makefile.

Stuart Marks has updated the pull request incrementally with one additional commit since the last revision:

  Keep paragraph as a single line (per Jesper).

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Changes:
  - all: https://git.openjdk.org/guide/pull/148/files
  - new: https://git.openjdk.org/guide/pull/148/files/a9f26da3..cfdad340

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=guide&pr=148&range=01
 - incr: https://webrevs.openjdk.org/?repo=guide&pr=148&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/guide/pull/148.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/148/head:pull/148

PR: https://git.openjdk.org/guide/pull/148