Format of HP 95LX menu data:
Offset	Size	Description	)
 00h 80 BYTEs	first line of menu text
 50h 80 BYTEs	second line of menu text
 A0h 80 BYTEs	third line of menu text
 F0h	WORD	number of keywords
 F2h	WORD	index of currently highlighted keyword or FFFFh
 F4h	WORD	single prompt on top line if nonzero
 F6h 20 BYTEs	which line each of 20 keywords is located on
10Ah 20 BYTEs	offset of each of 20 keywords within its line
11Eh 20 BYTEs	length of each of 20 keywords
132h 20 BYTEs	first letter of each of 20 keywords
146h 20 WORDs	offsets of long prompts for each of 20 keywords