INT 4B - Virtual DMA Specification - SCATTER/GATHER LOCK REGION
        AX = 8105h
        DX = flags
            bits 0-5 reserved (zero)
            bit 6: EDDS should be returned with page table entries
            bit 7: only present pages should be locked (not-present pages
                        receive entry of 0000h)
            bits 8-15 reserved (zero)
        ES:DI -> Extended DMA descriptor structure (see AX=8102h)
                region size, linear segment, linear offset, and number avail
                fields set
Return: CF clear if successful
            EDDS number used field set
            if DX bit 6 set, lower 12 bits of BX = offset in first page
        CF set on error
            AL = error code (see AX=8102h)
            EDDS region size field filled with max length in bytes that can be
                locked and described in the EDDS table
BUG:    Windows 3.0 in enhanced mode may return zero instead of the physical
          page address for pages which were originally not present
SeeAlso: AX=8103h,AX=8106h

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