[tex-hyphen] hyphenation with ligatures in input

[Arthur Reutenauer]

> /Characters/ ... : yes.  But consider a Unicode-in/Unicode-out
> preprocessor; might it not generate fi in the output stream,

  If it’s outputting characters, it shouldn’t generate fi or such like.
These characters have been introduced in Unicode for compatility with
existing standards (so as to have lossless conversion to and from these
standards), but their use is discouraged.  See for example:

	http://www.unicode.org/faq/ligature_digraph.html#Lig2

  If the process is outputting glyphs, it shouldn’t use Unicode
codepoints anyway.

	Arthur