(Alpha and I64 only.) The Put Invocation Registers routine
    modifies specified values in a procedure's invocation context.
    A procedure's invocation context consists of the values stored in
    the integer and floating-point registers as well as the program
    counter and the processor status registers.

    LIB$PUT_INVO_REGISTERS updates internal register save areas with
    the new values. These values are written to the active register
    set by the time control returns to the procedure asociated with
    the specified invocation handle.

    Format

      LIB$PUT_INVO_REGISTERS   invo_handle, invo_context, invo_mask