INT 2F - PRINDIR v9.0 - SET LOCK FILENAME                                       
	AX = 7F04h
	CX:DX -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. name of lock file
Return: AX = status
	    0000h successful
	    FFFFh invalid device number
SeeAlso: AX=7F00h"PRINDIR",AX=7F01h"PRINDIR",AX=7F03h"PRINDIR"
SeeAlso: AX=7F05h,AX=7F06h,AX=7F08h,AX=7F0Ah,AX=7F0Bh