- Add a missing release note for TCP high-water. That feature was not
yet merged when the initial version of !2524 was prepared and its
release note was missed when that merge request was later rebased.
- Rephrase the release note for CVE-2019-6477 so that it uses the same
text as its corresponding notes in all other releases.
- Unify whitespace in doc/arm/notes-9.15.6.xml.