re PR middle-end/28915 (ICE: tree check: expected class 'constant', have 'declaration' (var_decl) in build_vector, at tree.c:973)

        PR middle-end/28915
        * gimplify.c (gimplify_init_constructor): Don't reduce TREE_CONSTANT
        vector ctors.
        * tree-cfg.c (verify_expr): Don't look into TREE_CONSTANT
        vector ctors.
        * expmed.c (make_tree): Handle CONST, SYMBOL_REF.
        * tree.c (build_vector): Handle non-_CST elements.

Co-Authored-By: Andrew Pinski <pinskia@physics.uc.edu>

From-SVN: r118747