Add -enable-threads=gnat

[Laurent Guerby]

On Wed, 2003-04-23 at 03:38, Richard Kenner wrote:
>     Hum.  I'm surprised that GNAT uses its own thread library,
>     rather than the system library.  The later will be more
>     efficient on any reasonable target.
> 
> First of all, you may have a system which has more than one "system
> library", so this will force the use of the same one that Ada chose.
> 
> Also, there are many systems where the supplied thread library has bugs that
> the precise semantics of Ada expose (specifically Annex D), in which case
> an alternate library has to be used.
> 
> But I'll leave the details to the experts here, since I don't know that much
> about this area.  I do know this was done as a bugfix.  I also remember
> Laurent Guerby saying about a week ago that he needed this change in
> order to get something to work, so perhaps he can say more too.

I needed to add gthr-gnat.[ch] because s-tasini.adb unconditionally
import and call __gnat_install_locks, otherwise all
tasking programs were failing the link. No idea
on why the three other symbols are there.

-- 
Laurent Guerby <guerby@acm.org>