PR c++/9283
	PR c++/15000
	* c-common.c (c_common_attribute_table): Allow
	handle_visibility_attribute to be called for types.
	(handle_visibility_attribute) When given a type, set the visibility
	bits on the TYPE_NAME.  When given a decl, don't set no_add_attrs
	so that we can check later whether the attribute was present. Added
	warning if attribute applied to non class type.
	* c-decl.c (diagnose_mismatched_decls): Updated rules for merging
	decls and checking that they are consistent.
	* common.opt: Added -fvisibility.
	* c.opt, c-opts.c: Added -fvisibility-inlines-hidden.
	* c-pragma.h, c-pragma.c: Added handle_pragma_visibility().
	* flags.h, tree.h: Added assorted support defines for overall patch
	* opts.c: Added parsing support for -fvisibility.
	* tree.c (build_decl): Set visibility for all decls to be whatever
	is in force at that time.
	* varasm.c (default_binds_local_p_1): Reworked logic determining
	when to make a symbol locally bound.
	* doc/invoke.texi: Added documentation for -fvisibility and
	-fvisibility-inlines-hidden.

	PR c++/15000
	PR c++/9283
	* class.c (check_field_decls): Apply hidden visibility if
	-fvisibility-inlines-hidden and inlined unless otherwise specified
	(build_vtable): Set vtable visibility to class visibility.
	(check_field_decls): Default static member visibility to class
	visibility.
	(check_methods): Default method visibility to class visibility.
	* cp-tree.h: Added CLASSTYPE_VISIBILITY and
	CLASSTYPE_VISIBILITY_SPECIFIED macro.
	* decl.c (duplicate_decls): New logic for merging definition decls
	with declaration decls. Added ignore & warning when non default
	applied to global operator new or delete.
	* method.c, optimize.c, rtti.c: Added setting of VISIBILITY_SPECIFIED
	wherever VISIBILITY was changed
	* rtti.c (get_tinfo_decl): Set typeinfo visibility to class
	visibility.
	(tinfo_base_init): Set typeinfo name visibility to class visibility.

	PR c++/9283
	PR c++/15000
	* gcc.dg/visibility-9.c, gcc.dg/visibility-a.c: New tests.
	* g++.dg/ext/visibility/: New directory.
	* g++.dg/ext/visibility-1.C, g++.dg/ext/visibility-2.C
	g++.dg/ext/visibility-3.C, g++.dg/ext/visibility-4.C,
	g++.dg/ext/visibility-5.C, g++.dg/ext/visibility-6.C,
	g++.dg/ext/visibility-7.C: Move to g++.dg/ext/visibility/.
	* g++.dg/ext/visibility/fvisibility.C,
	g++.dg/ext/visibility/fvisibility-inlines-hidden.C,
	g++.dg/ext/visibility/fvisibility-override1.C
	g++.dg/ext/visibility/fvisibility-override2.C
	g++.dg/ext/visibility/memfuncts.C
	g++.dg/ext/visibility/noPLT.C
	g++.dg/ext/visibility/pragma.C
	g++.dg/ext/visibility/pragma-override1.C
	g++.dg/ext/visibility/pragma-override2.C
	g++.dg/ext/visibility/staticmemfuncts.C
	g++.dg/ext/visibility/virtual.C: New tests.

Co-Authored-By: Brian Ryner <bryner@brianryner.com>

From-SVN: r85167