INT 2C P - RM386 v6.00 - CLOAKING - CALL V86-MODE PROCEDURE
        AX = 0025h
        DS:EBX -> client register structure (see AX=0009h)
Return: CF clear if successful
            client register structure updated
        CF set if no more nested procedure call space available
Note:   this call uses the V86-mode stack supplied in the client structure, and
          calls the routine specified by CS:IP in the client structure
SeeAlso: AX=0026h,AX=0027h,INT 31/AX=0301h

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