Making atexit weak does nothing for dynamicly linked apps. And for

Making atexit weak does nothing for dynamicly linked apps.  And for
staticly linked apps it entirely prevents destructors from running
unless atexit is called for some other reason.  So if they enabled
ctor/dtor support we need to have a call to the real atexit for
dtors to work properly.  If people don't want the extra 4k or so
of junk in their static apps, they should leave ctor/dtor support
disabled.
 -Erik