[Bug ada/125695] Big_Exp special case for (+/-)2 ** K is broken for -2 and even K

[liam at liampwll dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125695

--- Comment #9 from Liam Powell <liam at liampwll dot com> ---
s/-11 mod 5/11 mod -5 ...