Fix lang matching logic

Previous code was broken logically, but harmless.

src/hb-ot-tag.cc

@@ -845,7 +845,7 @@ hb_ot_tag_from_language (hb_language_t language)
     {
       const LangTagLong *lang_tag;
       lang_tag = &ot_languages_zh[i];
-      if (lang_matches (lang_tag->language, lang_str))
+      if (lang_matches (lang_str, lang_tag->language))
 	return lang_tag->tag;
     }
 

test/api/test-ot-tag.c

@@ -195,6 +195,7 @@ test_ot_tag_language (void)
 
   test_language_two_way ("ZHH", "zh-hk"); /* Chinese (Hong Kong) */
 
+  test_tag_from_language ("ZHS", "zh"); /* Chinese */
   test_tag_from_language ("ZHS", "zh-cn"); /* Chinese (China) */
   test_tag_from_language ("ZHS", "zh-sg"); /* Chinese (Singapore) */
   test_tag_from_language ("ZHT", "zh-mo"); /* Chinese (Macao) */