Map zh-Hant-HK to ZHH

Fixes https://github.com/behdad/harfbuzz/issues/300

src/hb-ot-tag.cc

@@ -826,16 +826,18 @@ static const LangTag ot_languages[] = {
 };
 
 typedef struct {
-  char language[8];
+  char language[11];
   hb_tag_t tag;
 } LangTagLong;
 static const LangTagLong ot_languages_zh[] = {
+  /* Store longest-first, if one is a prefix of another. */
   {"zh-cn",	HB_TAG('Z','H','S',' ')},	/* Chinese (China) */
   {"zh-hk",	HB_TAG('Z','H','H',' ')},	/* Chinese (Hong Kong) */
   {"zh-mo",	HB_TAG('Z','H','T',' ')},	/* Chinese (Macao) */
   {"zh-sg",	HB_TAG('Z','H','S',' ')},	/* Chinese (Singapore) */
   {"zh-tw",	HB_TAG('Z','H','T',' ')},	/* Chinese (Taiwan) */
   {"zh-hans",	HB_TAG('Z','H','S',' ')},	/* Chinese (Simplified) */
+  {"zh-hant-hk",HB_TAG('Z','H','H',' ')},	/* Chinese (Hong Kong) */
   {"zh-hant",	HB_TAG('Z','H','T',' ')},	/* Chinese (Traditional) */
 };