[truetype] Some variable renamings.

Too much local variables holding different structures were called
`metrics'.

* src/truetype/ttdriver.c (tt_size_select): s/metrics/size_metrics/.

* src/truetype/ttgload.c (tt_get_metrics_incr_overrids,
compute_glyph_metrics): s/metrics/incr_metrics/.
(load_sbit_image): s/metrics/sbit_metrics/.

* src/truetype/ttobjs.c (tt_size_run_fpgm): s/metrics/size_metrics/.
(tt_size_init_bytecode): s/metrics/tt_metrics/.
(tt_size_reset): s/metrics/size_metrics/.
4 files changed