[subset] small cleanups in hb-ot-os2-table.

src/hb-ot-os2-table.hh

@@ -83,8 +83,9 @@ struct os2
     for (unsigned int i = 0; i < codepoints.len; i++)
     {
       hb_codepoint_t cp = codepoints[i];
-      int bit = hb_get_unicode_range_bit (cp);
-      if (bit >= 0 && bit < 128) {
+      unsigned int bit = hb_get_unicode_range_bit (cp);
+      if (bit < 128)
+      {
         unsigned int block = bit / 32;
         unsigned int bit_in_block = bit % 32;
         unsigned int mask = 1 << bit_in_block;

src/hb-ot-os2-unicode-ranges.hh

@@ -230,7 +230,7 @@ _compare_range (const void *_key, const void *_item, void *_arg)
  * hb_get_unicode_range_bit:
  * Returns the bit to be set in os/2 ulUnicodeRange for a given codepoint.
  **/
-static int
+static unsigned int
 hb_get_unicode_range_bit (hb_codepoint_t cp)
 {
   Range *range = (Range*) hb_bsearch_r (&cp, os2UnicodeRangesSorted,