init_end
Description:
Initializes a `PangoGlyphItemIter` structure to point to the last cluster in a glyph item.
See `PangoGlyphItemIter` for details of cluster orders.
Parameters:
| this | a `PangoGlyphItemIter` | 
| glyph_item | the glyph item to iterate over | 
| text | text corresponding to the glyph item | 
Returns:
| false if there are no clusters in the glyph item |