i am 99% of the way towards beginning to try to compile unicode-internal :)
currently we use 32-127 for the values of the chars in the iso-8859
charsets. maybe that was needed under old-mule, but in unicode-internal
charsets can have values in any arbitrary interval or rectangle in 256
or 256x256 space. shouldn't we use 160-255? this would only matter in
the output of `split-char'; `make-char' already goes either way.