[Bug tree-optimization/58689] Enhance returns_nonnull

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58689
Bug 58689 depends on bug 24825, which changed state.

Bug 24825 Summary: Standard runtime methods that are known to not return null should not trigger null checks.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24825

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |WONTFIX