INT 60 u - HP 95LX System Manager - CLEAR PORTION OF SCREEN
        DI = 0301h
        STACK:  2 WORDs unused dummies (for calls from high level languages)
                WORD    starting row (-3 is topmost, 0 is first user line)
                WORD    starting column
                WORD    number of rows
                WORD    number of columns
Return: ???
        STACK unchanged
SeeAlso: INT 60/DI=0302h,INT 60/DI=1005h