INT 21 - DOS 3+ - GET CURRENT PSP ADDRESS
        AH = 62h
Return: BX = segment of PSP for current process
Notes:  under DOS 3+, this function does not use any of the DOS-internal stacks
          and may thus be called at any time, even during another INT 21h call
        the current PSP is not necessarily the caller's PSP
        identical to the undocumented AH=51h
SeeAlso: AH=51h