[PATCH v3] Linux: Remove <sys/sysctl.h> and the sysctl function

[Florian Weimer]

* Adhemerval Zanella via Libc-alpha:

> Ok. Usually when it requires more than one exception implementation
> with exact same behaviour, this might be an indication to move this 
> option on the generic implementation and add a arch-defined flag to
> enable it (I don't have a strong opinion here).

I tried this first, but it is more complicated.  The simplification
only kicks in at three similar cases.  (x32 needs something else
again, so it does not count here).