Function  3Ah   Remove Subdirectory  (RMDIR) 
entry   AH      3Ah 
	DS:DX   address of ASCIIZ pathname string 
return  CF      clear     successful 
		set       AX      error code if any  (3, 5, 16) 
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