Hi everyone, 

Here is a better version of the patch. 
All tests are on Linux are passing. Few have been disabled as 
they are working only with GNU model. 
For AIX, few failures remains. I haven't XFAIL them yet, as I 
want to know if they AIX only or related to the model itself. 

A few part still need to be improved (dg-require-localmodel,
std::locale:global, FreeBSD specific #ifdef). 
But at least it can be tested in most of the platforms as is. 

Note that I'll stop working on it until gcc12. Mostly because gcc
is on freeze but also because I've more urgent stuff to do right now. 
Of course any feedbacks is welcome ! But I might not send a
new patch if it requires too much time (at least not right now). 

Thanks anyway Rainer and Jonathan for your help ! I hope this 
version suits you better !

Clément