Function  39h   Create Subdirectory (MKDIR) 
		Makes a subdirectory along the indicated path 
entry   AH      39h 
	DS:DX   address of ASCIIZ pathname string 
return  flag CF 0       successful 
		1       error 
			AX      error code if any  (3, 5)  
note 1) The ASCIIZ string may contain drive and subdirectory. 
     2) Drive may be any valid drive (not nescessarily current drive) 
     3) The pathname cannot exceed 64 characters