cl_sortkey should be 230 bytes long, not 255

cl_sortkey should be 230 bytes long, not 255

Bug 25503, reported by Dmitriy.  When switching it to binary, I figured
that since it would always be one byte per character now, there would be
room to make it the full 255 bytes.  In fact, if cl_to is utf8, the
(cl_to, cl_type, cl_sortkey, cl_from) index will be 255*3 + 1 + 255 + 4
= 1025 bytes, longer than the max of 1000.  Shortening cl_sortkey to 230
bytes fixes this (fix tested by Dmitriy).

I didn't add an updater because if you're already running the current
schema without problems, you don't need this change.