bug#16731: 24.3.50; Latin small letter sharp s is not considered lower-case

[Eli Zaretskii]

> Date: Thu, 13 Feb 2014 19:02:08 +0100
> From: Andreas Röhler <andreas.roehler@easy-emacs.de>
> CC: 16731@debbugs.gnu.org
> 
> Maybe I'm missing the point: all change needed is not to store "ß" into the 
> uppercase-table.
> Why not store nil there instead?

Because that's not what case tables are documented to hold.  We will
break back compatibility if we put nil there.