Lseek

LSEEK

rax	19	Move the filepointer	8 bit
rbx	fd	a file descriptor	16 bit
rcx	offset	offset for use	32/64 bit (off_t)
rdx	wehnce	what to do with the offset	2 bit
	0	SEEK_SET : the offset given is set.
	1	SEEK_CUR : the offset is added to the curent position.
	2	SEEK_END : the offset is set in relation to the end of the file.

On return	rax
	new position /errorcode

With an offset value of 0 you get with SEEK_CUR the curent position
and with SEEK_END the file length.
Use NEG to generate negative system independent values.

Errorcode	c++ name	Description
9	EBADF	Bad file number
22	EINVAL	Invalid argument
29	ESPIPE	Illegal seek

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