Saves another 2.5kb.

Part of https://github.com/harfbuzz/harfbuzz/issues/1652

Part of https://github.com/harfbuzz/harfbuzz/issues/1652

Saves another 12kb:

$ python ./gen-ucd-table.py ucd.nounihan.grouped.zip > hb-ucd-table.hh && make -j5 CPPFLAGS='-Os -DHB_TINY' -C ~/hb/build/src/  && size ~/hb/build/src/.libs/libharfbuzz_la-hb-ucd.o
INFO: Loading UCDXML...
INFO: Preparing data tables...
INFO: Generating output...
INFO:   Compression=1:
INFO:       Dataset=gc       FullCost=18612
INFO:       Dataset=ccc      FullCost=3550
INFO:       Dataset=bmg      FullCost=1548
INFO:       Dataset=sc       FullCost=17765
INFO:       Dataset=dm       FullCost=13325
INFO:   Compression=3:
INFO:       Dataset=gc       FullCost=10726
INFO:       Dataset=ccc      FullCost=2389
INFO:       Dataset=bmg      FullCost=1052
INFO:       Dataset=sc       FullCost=13669
INFO:       Dataset=dm       FullCost=7780
INFO:   Compression=5:
INFO:       Dataset=gc       FullCost=8274
INFO:       Dataset=ccc      FullCost=2055
INFO:       Dataset=bmg      FullCost=908
INFO:       Dataset=sc       FullCost=4073
INFO:       Dataset=dm       FullCost=7780
INFO: Done.

Part of https://github.com/harfbuzz/harfbuzz/issues/1652

https://github.com/harfbuzz/harfbuzz/issues/1652

UCDN was ~120kb of data.  New implementatoin is 69kb in default builds,
and 49kb if built with HB_OPTIMIZE_SIZE or __OPTIMIZE_SIZE__.  The
latter automatically enabled if built with -Os or -Oz.

There's room to shave off another 10kb or 20kb.  That will follow later.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1652