MsDos procedure

  DECLARATION:  MsDos(var Regs : Registers);

      PURPOSE:  Executes a DOS function call

         UNIT:  DOS

      REMARKS:  Calling MsDos will achieve the same results as a call to
                Intr with an IntNo of $21.  Registers is declared in the
                DOS Unit as follows:

                Type
                   Registers = Record
                                 Case Integer of
                                    0 : (AX,BX,CX,DX,BP,SI,DI,DS,ES
                                         Flags : Word);
                                    1 : (AL,AH,BL,BH,CL,CH,DL,DH : Byte);
                               End;

  DIFFERENCES:  In 3.0, there was no type checking performed on the
                Registers parameter.