[Bug c++/82269] -Wignored-qualifiers should not trigger on templated code

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82269

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I agree that in this case the caller is wrong and should do pointer_cast<T> not
pointer_cast<const T>. The warning found a bug.

In general the warning is a bit too noisy, but we already have a bug report
about it.