Removes a branch from a transaction and returns the outcome of
    the transaction. $END_BRANCHW always waits for the request to
    complete before returning to the caller. Other than this, it is
    identical to $END_BRANCH.
    Format
      SYS$END_BRANCHW  [efn] ,[flags] ,iosb ,[astadr] ,[astprm] ,tid
                       ,bid
    C Prototype
      int sys$end_branchw  (unsigned int efn, unsigned int
                           flags, struct _iosb *iosb, void
                           (*astadr)(__unknown_params), int astprm,
                           unsigned int tid [4], unsigned int bid
                           [4]);