labels: if we have overridden EXTERN, don't call define_label()
labels: if we have overridden EXTERN, don't call define_label()

If we have overridden EXTERN, then we should not call define_label()
on it again.  Return a fail status from declare_label(), indicating
that the type declaration failed, but of course we don't print an
error message.

Signed-off-by: H. Peter Anvin (Intel) <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm