`VarDumper::export()` applied over framework.
Handle invalid code sequences in Html::encode()
Changelog update
Merge pull request #3518 from DaSourcerer/invalid-chars-in-htmlspecialchars-handling

Handle invalid code sequences in Html::encode()
Merge pull request #3517 from klimov-paul/apply-var-dumper-var-export

`VarDumper::export()` applied over framework.