Wrote all remaining Unicode input and output functions.

Updated gestalt to support Unicode.
Split off functions to convert from one character set to another and put them in charset.c.

glk_put_char_uni(), glk_put_string_uni(), glk_put_buffer_uni(),
glk_put_char_stream_uni(), glk_put_string_stream_uni(),
glk_put_buffer_stream_uni(), glk_get_char_stream_uni(),
glk_get_buffer_stream_uni(), glk_get_line_stream_uni()

git-svn-id: http://lassie.dyndns-server.com/svn/gargoyle-gtk@29 ddfedd41-794f-dd11-ae45-00112f111e67