[Groff] caching result of charinfo::get_flags

[Werner LEMBERG]

Colin, Daiki-san,


if there are a lot of character classes, the frequently used function
`charinfo::get_flags' can get expensive.  Any idea how to cache its
return value?  Essentially, it needs to be computed only once, but as
soon as `.class' is called again, it has to be recomputed (again, only
once)...

Perhaps calling `.class' should simply trigger recomputation of all
charinfos in the dictionary?


    Werner