#54093, add language in language preference

pref-languages-add.xul
pref-languages.js
pref-languages.properties
makefile.win
MANIFEST
jar.mn

p = adrian havill
r = shanjian
sr = blizzard

This file contains a message used by add language dialogue box.

xpfe/components/prefwindow/resources/locale/en-US/pref-languages.properties

@@ -0,0 +1 @@
+illegalOtherLanguage=Not a valid language code.