Fix raqm_set_text_utf8/utf16 reading beyond len for multibyte

_raqm_u8_to_u32 and _raqm_u16_to_u32 were only incrementing in_len instead of
increasing it by the amount of bytes/shorts read. Fix so raqm_set_text_utf8 and
raqm_set_text_utf16 correctly interpret the len parameters as UTF-8
bytes/UTF-16 shorts

src/raqm.c

@@ -581,9 +581,10 @@ _raqm_u8_to_u32 (const char *text, size_t len, uint32_t *unicode)
 
  while ((*in_utf8 != '\0') && (in_len < len))
  {
- in_utf8 = _raqm_get_utf8_codepoint (in_utf8, out_utf32);
+ const char *out_utf8 = _raqm_get_utf8_codepoint (in_utf8, out_utf32);
+ in_len += out_utf8 - in_utf8;
+ in_utf8 = out_utf8;
  ++out_utf32;
- ++in_len;
  }
 
  return (out_utf32 - unicode);
@@ -628,9 +629,10 @@ _raqm_u16_to_u32 (const uint16_t *text, size_t len, uint32_t *unicode)
 
  while ((*in_utf16 != '\0') && (in_len < len))
  {
- in_utf16 = _raqm_get_utf16_codepoint (in_utf16, out_utf32);
+ const uint16_t *out_utf16 = _raqm_get_utf16_codepoint (in_utf16, out_utf32);
+ in_len += (out_utf16 - in_utf16);
+ in_utf16 = out_utf16;
  ++out_utf32;
- ++in_len;
  }
 
  return (out_utf32 - unicode);