INT 21 - LANtastic - COPY FILE
AX = 5F97h
CX:DX = number of bytes to copy (FFFFFFFFh = entire file)
SI = source file handle
DI = destination file handle
Return: CF clear if successful
DX:AX = number of bytes copied
CF set on error
AX = error code
Note:   copy is performed by server

215F97 - LANtastic - COPY FILE