[Bug c/70952] Missing warning for likely-erroneous octal escapes in string literals

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70952

--- Comment #2 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
Bah, please disregard the last point; '\9' is diagnosed similar to "\9".