Import

This is to make Medhi's commits about extern import work.
It depends. Are you speaking about : 
```C
#include <iostream>                                                                
                                                                                   
int foo(int i){ return i;}                                                         
                                                                                   
extern "C" int _Z3fooi(){ return 2;}                                               
                                                                                   
int main() {                                                                       
    std::cout << foo(1);                                                           
    return 1;                                                                      
}     
```
Or about variables created in gcc/clang for omp scheduling for example (__i and __j if I correctly remember)?

I agree it doesn't cost but it look overkill and make the code less readable compare to this convension. Also, Python use __keyword when it should not be use/overwritten so it could be a good solution to make sure it is not use by users.