[Bug tree-optimization/86701] Optimize strlen called on std::string c_str()

[david.bolvansky at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86701

--- Comment #2 from Dávid Bolvanský <david.bolvansky at gmail dot com> ---
There is not string analysis to tell us that string has no null characters in
the middle?