Another patch for visibility.

[NIIBE Yutaka]

H.J and Martin, thanks for your comments and encouragement.

For the record, my initial implementation was (only for hidden):
	http://gcc.gnu.org/ml/gcc-patches/2000-05/msg01301.html

  > 	__attribute__ ((visibility(internal)))
  > 	__attribute__ ((visibility(hidden)))
  > 	__attribute__ ((visibility(protected)))

And this syntax was suggested by Richard Hendarson.  I should have
mentioned this in the prior mail.
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