Given an invocation context block and a quadword IP value in
    ip_copy, write the ip_copy value to the invocation context
    block IP and then use LIB$X86_PUT_INVO_REGISTERS to write to
    the actual context. The invocation context block remains
    unchanged if the routine fails. LIB$X86_SET_IP fails if
    LIB$X86_PUT_INVO_REGISTERS fails.

    Format
      LIB$X86_SET_IP (invo_context, ip_copy)