INT 21 - DOS 2+ - "CHDIR" - SET CURRENT DIRECTORY
	AH = 3Bh
	DS: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. pathname to become current directory (max 64 bytes)
Return: CF clear if successful
	    AX destroyed
	CF set on error
	    AX = error code (03h) (see #01680 at AH=59h/BX=0000h)
Notes:	if new directory name includes a drive letter, the default drive is
	  not changed, only the current directory on that drive
	changing the current directory also changes the directory in which
	  FCBsee File Control Block file calls operate
	under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=47h,AX=713Bh,INT 2F/AX=1105h