Debug checks and constexpr

[François Dumont]

Hi

     With recent additions of _GLIBCXX14_CONSTEXPR on a number of algos 
came regressions in debug mode. This is not the first time we have this 
kind of issue and surely won't be the last.

     So I can only think about one way to make it work. We should be 
able to tell the compiler to ignore debug checks when called in a const 
expression context. Is there already a way to do so ? If not is there 
any plan to do something similar ? Or anyone can think of a different 
way to deal with this problem ?

François