PR c/13134
* c--decl.c (duplicate_decls): Copy visibility flag when appropriate.
* cp/decl.c (duplicate_decls): Copy visibility flag when appropriate.
* testsuite/lib/gcc-dg.exp (dg-require-visibility): Define.
* testsuite/lib/target-supports (check_visibility_available): Define.
* testsuite/gcc.dg/visibility-1.c: New test.
* testsuite/gcc.dg/visibility-2.c: Likewise.
* testsuite/gcc.dg/visibility-3.c: Likewise.
* testsuite/gcc.dg/visibility-4.c: Likewise.
* testsuite/gcc.dg/visibility-5.c: Likewise.
* testsuite/gcc.dg/visibility-6.c: Likewise.
* testsuite/g++.dg/ext/visibility-1.C: Likewise.
* testsuite/g++.dg/ext/visibility-2.C: Likewise.
* testsuite/g++.dg/ext/visibility-3.C: Likewise.
* testsuite/g++.dg/ext/visibility-4.C: Likewise.
* testsuite/g++.dg/ext/visibility-5.C: Likewise.
* testsuite/g++.dg/ext/visibility-6.C: Likewise.

From-SVN: r74487