mktables: Calculate legal chars in algorithmic names

mktables: Calculate legal chars in algorithmic names

Many ideographic character names are of the form 'prefix-code_point'.
For these, we know that the legal names are just the ones in the prefix,
the dash, and uppercase hex digits.  This commit for each series of
these types of names figures out what characters are legal in that
series, and adds that info to the hash describing the series.  This will
be used in a later commit to rule out entire series when matching
under some circumstances, without having to try any individual matches
within it.