[Bug c/65106] C99 intialization of struct with const member through a non-const pointer

[andrii.riabushenko at barclays dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65106

--- Comment #2 from Andrey Riabushenko <andrii.riabushenko at barclays dot com> ---
Thanks Joseph for pointing out relevant standard sections, hence standard does
not allow for that.

Given that implicit copies of structs with constant members are happening today 
(pass as argument by value and return value) and some compilers do support it,
can we consider this as compiler extension?