cleaning the generic module :)

[Frederic-Emmanuel PICCA]

>
>
>>4) I removed the redondant flags '-D_XOPEN_SOURCE=500', '-D_BSD_SOURCE',
>> when '-D_GNU_SOURCE' is use.
>>    
>>
>
>On Mac OS X, -D_GNU_SOURCE does not do anything, but -D_XOPEN_SOURCE
>most definitely does, I can only assume similar things for _BSD_SOURCE
>and the *BSDs, I'd bet they should all still be there.  Not every
>platform is Linux.  ;)
>  
>

So this must be put in the osx/detect_generic.py is'nt it ?