Fix the lexer to reject unescaped control characters in JSON strings,
in accordance with RFC 8259 "The JavaScript Object Notation (JSON)
Data Interchange Format".
Bonus: we now recover more nicely from unclosed strings. E.g.
{"one: 1}\n{"two": 2}
now recovers cleanly after the newline, where before the lexer
remained confused until the next unpaired double quote or lexical
error.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180823164025.12553-19-armbru@redhat.com>
340db1ed82