[truetype] Apply MVAR hasc, hdsc and hlgp metrics to current FT_Face metrics. Instead of setting typo or win metrics as the new FT_Face metrics indiscriminately, apply only typo deltas to the currently active FT_Face metrics. This prevents line height differences when e.g. the default outlines were used as the regular face and instances for everything else. * src/truetype/ttgxvar.c (tt_apply_mvar): Implement.