unicode: Support diacritic marks > 0xffff (disabled for now)
* Terminating record of the max unicode codepoint (0x10ffff)
* Add in Arabic diacritic marks in the 0x10efa..10efff range
This is currently disasbled due to it effectively doubling the
size of our diacritic table. The diacritics added are unlikely
to be seen in practice as they are used only in some formal
Quaranic contexts. If we identify other diacritic marks above
0xffff, then we can turn this code on.
Change-Id: I50c2eace18c70be6fe7199fccab190e7da401089