Infrastructure changes for character set support. ustrtoa,

Infrastructure changes for character set support. ustrtoa,
ustrfroma, utoa_dup and ufroma_dup now take a charset parameter, and
also have a variety of subtly distinct forms. Also, when a \cfg
directive is seen in the input file, the precise octet strings for
each parameter are kept in their original form as well as being
translated into Unicode, so that when they represent filenames they
can be used verbatim.

git-svn-id: svn://svn.tartarus.org/sgt/halibut@4097 cda61777-01e9-0310-a592-d414129be87e