prefer apple last resort glyphs
Described at <http://developer.apple.com/fonts/LastResortFont/>
for a more uniform style:
> Unicode blocks are illustrated by a representative glyph from the block,
> chosen to be as distinct as possible from glyphs of other blocks.
>
> Examplar glyphs were chosen in a number of ways. Almost all of the
> Brahmic scripts show the initial consonant ka. Latin uses the letter A
> because it's the first letter, and because in each Latin block there is
> a letter A so they can be easily differentiated. Greek and Cyrillic use
> their last letters, omega and ya, because they are so distinctive. Most
> other alphabets and syllabaries use their initial letter where
> distinctive.
Try to avoid unnecessary exceptions, though in some cases I can't help but
know better (usually improving distinctiveness, especially considering
unknown output variants).
Restrict to a single entry per 0x80, mostly keeping the latest unicode
version for maximum effort.