Changelog markup fixes, refs #682

Release 3.39

Refs #688

Fix underline length, refs #656

Release 3.38

Refs #628, #633, #643, #644

Release 3.38a0

Refs #643

Release 3.37

Refs #618, #619, #620, #621, #630, #632

Release 3.36

Refs #344, #604, #606

More 3.35.2 release notes

Refs #433, #522, #596, #598

Release notes for 3.35.1, refs #592

Fixed two typos in the release notes