Translations: Add hu, zh_CN, and zh_TW.

I made a few white space changes to these without getting them
approved by the translation teams. (I tried to contact the hu and
zh_TW teams but didn't succeed. I didn't contact the zh_CN team.)

po/LINGUAS

@@ -2,7 +2,8 @@
 de
 fi
 fr
+hu
 it
 pl
 pt_BR
 vi
@@ -5,4 +6,6 @@
 it
 pl
 pt_BR
 vi
+zh_CN
+zh_TW