INT 2F - WinDOS v2.11 - GET MAIN SHELL PSPsee Program Segment Prefix
	AX = AF0Ah
Return: AX = shell's PSPsee Program Segment Prefix (same as DS on last call to AX=AF06h)
Desc:	get the PSPsee Program Segment Prefix address of the last program to call AX=AF06h (normally
	  the main command interpreter)
SeeAlso: AX=AF00h"WinDOS",AX=AF06h"WinDOS",AX=AF09h