Darwin: Make metadata symbol lables linker-visible for GNU objc.

Darwin: Make metadata symbol lables linker-visible for GNU objc.

Now we have shifted to using the same relocation mechanism as clang for
objective-c typeinfo the static linker needs to have a linker-visible
symbol for metadata names (this is only needed for GNU objective C, for
NeXT the names are in separate sections).

gcc/ChangeLog:

	* config/darwin.h
	(darwin_label_is_anonymous_local_objc_name): Make metadata names
	linker-visibile for GNU objective C.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>