This allows us more options when determining whether to use a
pre-composed character or not:
We now only use the pre-composed character if it's from the primary
font, or if at least one of the base or combining characters are from
a fallback font.
I.e. use glyphs from the primary font if possible. But, if one or more
of the decomposed glyphs are from a fallback font, use the
pre-composed character anyway.
We only used utf8proc to try to pre-compose a glyph from a base and
combining character.
We can do this ourselves by using a pre-compiled table of valid
pre-compositions. This table isn't _that_ big, and binary searching it
is fast.
That is, for a very small amount of code, and not too much extra RO
data, we can get rid of the utf8proc dependency.
