INT 21 - DOS 3+ - CREATE NEW FILE
        AH = 5Bh
        CX = file attribute (see AX=4301h)
        DS:DX -> ASCIZ filename
Return: CF clear if successful
            AX = file handle opened for read/write in compatibility mode
        CF set on error
            AX = error code (03h,04h,05h,50h) (see AH=59h)
Notes:  unlike AH=3Ch, this function will fail if the specified file exists
          rather than truncating it; this permits its use in creating semaphore
          files because it is an atomic "test and set" operation
        under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
SeeAlso: AH=5Ah