[Bug middle-end/127785] [15/16/17 Regression] !__builtin_isunordered (a, b) & (a != b) folded to LTGT raises FE_INVALID for a quiet NaN since r15-3353

[ishevlyakov at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127785

--- Comment #6 from Igor Shevlyakov <ishevlyakov at gcc dot gnu.org> ---
I've restructured the patch (v2) as 2 series:
- backportable condition change (for 15/16 application)
- full removal from trunk