Verifies that a proxy exists and returns a valid local user for
    the caller to use to create a local login.

    Format

      SYS$VERIFY_PROXY  rem_node ,rem_user ,[proposed_user]

                        ,local_user ,local_user_length ,[flags]

    C Prototype

      int sys$verify_proxy  (void *rem_node, void *rem_user, void

                            *proposed_user, void *local_user,

                            unsigned short int *local_user_len,

                            unsigned int flags);