[Bug c/84764] Wrong warning "so large that it is unsigned" for __int128 constant

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84764

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
__int128 is not an extended integer type in the C sense.  The main reason is
because intmax_t is not defined as __int128.