INT 31 P - DPMI 0.9+ - FREE LDT DESCRIPTOR
        AX = 0001h
        BX = selector to free
Return: CF clear if successful
        CF set on error
            AX = error code (DPMI 1.0+) (8022h) (see AX=0000h)
Notes:  only one descriptor is freed per call
        the program's initial CS, DS, and SS descriptors may be freed
        (DPMI 1.0+) any segment registers containing the freed selector are
          set to 0000h
        not supported by MS Windows 3.0 in Standard mode
SeeAlso: AX=000Ah,AX=000Dh,INT 21/AX=3502h