PR c++/28407
        * cp/decl.c (grokvardecl): Set DECL_THIS_STATIC on file-scope
        const variables with implicit internal linkage.
        * cp/tree.c (decl_linkage): Only return lk_external if it's set.

        PR c++/28409
        * cp/decl2.c (constrain_visibility): Ignore the anonymous namespace 
        for extern C decls.
        (VISIBILITY_STATIC): Rename to VISIBILITY_ANON.

        Don't override explicit visibility.
        * cp/decl2.c (constrain_visibility): Remove specified and reason
        parameters.  Don't touch decls that already have explicit visibility.
        (determine_visibility): Do copy DECL_VISIBILITY_SPECIFIED from
        template.
        (determine_visibility_from_class): Reverse sense of
        DECL_VISIBILITY_SPECIFIED test for target-specific visibility rules.
        (constrain_class_visibility): Only complain about member visibility
        if the member type is another class.  Don't change visibility of the
        current class.
        * tree.c (remove_attribute): New fn.
        * tree.h: Declare it.

From-SVN: r115622