* lib/charconv.c: (charconv_local8_to_utf8),
	(charconv_utf8_to_local8): tweaked the warnings to get more
	informations
	* lib/font.c: (font_get_suckfont): handled a potential case of
	uninitialised data being used (just paranoid)

	* objects/GRAFCET/boolequation.c: (opstring),
	(opblock_get_boundingbox), (opblock_draw),
	(boolequation_calc_boundingbox): some extra hoops needed now dia
	talks UTF8 (but gtk doesn't). More #hell. Beeek. Basically, the
	symbols can't yet be used with their proper Unicode cells, since
	gtk will demand them in the Symbol font, expressed in the local
	8-bit encoding.

	* samples/grafcet.dia: re-saved, now with a fixed bounding box (by
	the fix just above).