1. Remove the non-character special handling that makes them ignorable.
2. Ensure that FFFE and FFFF anywhere in a tailoring rule are invalid
3. Remove special entries from Fractional table. (Only do after 1)
4. Extend the 02 weights of FFFE to all levels (quaternary, identical)
5. Check which tables the FDD0+X and FDD1+X values need to be in, and remove them otherwise.
Only 1. is vital for the release; 2. is very important; the others can be postponed if necessary.
Items 1, 3 and 5 are done in ICU 4.6. Items 2 & 4 are covered by tickets #7898 and #8099.
Pseudo-contractions in FractionalUCA.txt starting with U+FDD0 are put into invuca.icu but not ucadata.icu. No change necessary.