We need this later on for MVAR also.
* src/truetype/ttgxvar.c (ft_var_load_delta_set_index_mapping): Add
parameters for delta-set index mapping and item variation store.
(ft_var_load_item_variation_store): Add parameter for item variation
store.
s/hvarData/varData/.
Move allocation of `hvar_table' to...
(ft_var_load_hvar): ...this function.
Updated.