Support the locale-supplied character set where appropriate. It's

Support the locale-supplied character set where appropriate. It's
used for converting command-line -C directives into Unicode; it's
used for outputting Unicode strings to stderr in error messages; and
it's used as the default character set for input files (although I'd
be inclined to recommend everyone use \cfg{input-charset} in all
their source files to ensure their portability).

git-svn-id: svn://svn.tartarus.org/sgt/halibut@4114 cda61777-01e9-0310-a592-d414129be87e