[Bug libstdc++/79141] [6/7 Regression] std::pair p = {}; fails to compile due to ambiguous overload

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79141

--- Comment #4 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Fixed on trunk so far, backporting...