Adds a new branch to a transaction.

    $START_BRANCHW always waits for the request to complete before
    returning to the caller. Other than this, it is identical to
    $START_BRANCH.

    Format

      SYS$START_BRANCHW  [efn] ,[flags] ,iosb ,[astadr] ,[astprm]

                         ,tid ,tm_name ,bid [,[timout] ,[acmode],

                         [tx_class]]

    C Prototype

      int sys$start_branchw  (unsigned int efn, unsigned int

                             flags, struct _iosb *iosb, void

                             (*astadr)(__unknown_params), int astprm,

                             unsigned int tid [4], void *tm_name,

                             unsigned int bid [4],...);