[Gnome-print] show() expects UTF-8 now

[Lauris Kaplinski <lauris helixcode com>]

Hello,

I changed gnome_print_show to expect UTF-8 encoded string, instead of
arbitrarily encode 8-bit one.

Also there is no more class method ::show(), but instead ::show_ucs4() and
corresponding general method:

gnome_print_show_ucs4 (GnomePrintContext * pc, guint32 * buf, gint length);

Everything seems to continue to work...

Lauris