"defined but not used" warning for .gnu.warning symbols

[Roland McGrath]

I'm using gcc from today's cvs to build current libc and for every
stub_warning it gives me a warning like this one:

../sysdeps/generic/shmctl.c:35: warning: `__evoke_link_warning_shmctl' defined but not used

Should we add the `unused' attribute to the symbol?  Is there something
that guarantees us gcc won't optimize out these defns entirely?