INT 2F U - DR DOS 5.0+ NLSFUNC - PREPARE CODE PAGE                              
	AX = 14FFh
	BX = code page (see #01757 at INT 21/AX=6602h)
Return: AX = ???
	ZF set if AX=0000h
Notes:	DR DOS 5.0 NLSFUNC returns CF set and AX=0001h if AL was not 00h, FEh,
	  or FFh on entry.
	passes codepage preparation request to each character device supporting
	  the generic IOCTL call
BUG:	DR DOS 5.0 NLSFUNC 3.00 - Novell DOS 7 NLSFUNC 3.03, and OpenDOS 7.01 -
	  DR-OpenDOS 7.02 NLSFUNC 3.02 requires DF cleared on entry, otherwise
	  the system may crash.  However, since this function is called only by
	  the BDOS, the problem never actually occurs.  DR-DOS 7.02/7.03
	  NLSFUNC 4.00+ always clears DF by itself.
SeeAlso: AX=1400h/BX=0EDCh,AX=14FEh,INT 21/AX=440Ch,INT 21/AX=6602h