[Bug libstdc++/122062] piecewise_linear_distribution(InputIteratorB, InputIteratorB, InputIteratorW) invokes comma operator

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122062

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Specifically, vector<double>::iterator. If it was vector<adl::trap>::iterator
it would need the fix. It doesn't hurt to make __normalize immune from evil
commas. It's a good habit to do it anywhere a for loop increments more than one
iterator.