INT 21 - DOS 2+ - "MKDIR" - CREATE SUBDIRECTORY
	AH = 39h
	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
Return: CF clear if successful
	    AX destroyed
	CF set on error
	    AX = error code (03h,05h) (see #01680 at AH=59h/BX=0000h)
Notes:	all directories in the given path except the last must exist
	fails if the parent directory is the root and is full
	DOS 2.x-3.3 allow the creation of a directory sufficiently deep that
	  it is not possible to make that directory the current directory
	  because the path would exceed 64 characters
	under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=3Ah,AH=3Bh,AH=6Dh,AX=7139h,AH=E2h/SF=0Ah,AX=43FFh/BP=5053h
SeeAlso: INT 2F/AX=1103h,INT 60/DI=0511h