INT 2F U - DOS 4.x only SHELLB.COM - COMMAND.COM interface                      
	AX = 1903h
	ES:DI -> 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. batch file name as for AX=1902h
Return: AL = status
	    FFh quoted batch file name matches last SHELLB parameter
	    00h it does not