(Alpha and I64 only.) The Get Current Invocation Context routine
    gets the current invocation context of any active procedure.

    A thread can obtain the invocation context of a current procedure
    using the following function format:

    Format

      LIB$GET_CURR_INVO_CONTEXT   invo_context

1  –  Returns

    None.

2  –  Argument

 invo_context

    OpenVMS usage:invo_context_blk
    type:         structure
    access:       write only
    mechanism:    by reference

    Address of an invocation context block into which the procedure
    context of the caller will be written.