[base] Clean up contour indexing. * src/base/ftoutln.c (FT_Outline_Reverse, FT_Outline_EmboldenXY, FT_Outline_Get_Orientation): Set the first and last indexes together. (FT_Outline_Decompose): Ditto and check them more stringently. * src/smooth/ftgrays.c (FT_Outline_Decompose)[STANDALONE_]: Ditto.