Add VEC_WIDEN_MULT_EVEN/ODD_EXPR

Add VEC_WIDEN_MULT_EVEN/ODD_EXPR

        * tree.def (VEC_WIDEN_MULT_EVEN_EXPR, VEC_WIDEN_MULT_ODD_EXPR): New.
        * cfgexpand.c (expand_debug_expr): Handle them.
        * expr.c (expand_expr_real_2): Likewise.
        * fold-const.c (fold_binary_loc): Likewise.
        * gimple-pretty-print.c (dump_binary_rhs): Likewise.
        * optabs.c (optab_for_tree_code): Likewise.
        * tree-cfg.c (verify_gimple_assign_binary): Likewise.
        * tree-inline.c (estimate_operator_cost): Likewise.
        * tree-pretty-print.c (dump_generic_node): Likewise.
        * tree.c (commutative_tree_code): Likewise.
        * tree-vect-generic.c (expand_vector_operations_1): Likewise.
        Handle type change before looking up optab.
        * optabs.h (OTI_vec_widen_umult_even, OTI_vec_widen_umult_odd): New.
        (OTI_vec_widen_smult_even, OTI_vec_widen_smult_odd): New.
        (vec_widen_umult_even_optab, vec_widen_umult_odd_optab): New.
        (vec_widen_smult_even_optab, vec_widen_smult_odd_optab): New.
        * genopinit.c (optabs): Initialize them.
        * doc/md.texi: Document them.

From-SVN: r189403