l10n: Correct Kurmanji ISO 639-3 code

And add a symlink ku symlink to it. Acording to wikipedia 80% of kurdish speaker understand this dialect. User can still select Sorani with proper locales setup

po/LINGUAS

@@ -38,8 +38,9 @@ ja
 ka
 kk
 km
+kmr
 ko
-kur
+ku
 lg
 lt
 lv

po/kur.po → po/kmr.po

@@ -1297,7 +1297,7 @@ msgstr "Tevgerên Mişkê"
 #. xgettext: Translate "C" to the language code: "fr", "en_GB", "nl", "ru"...
 #: src/libvlc.c:291
 msgid "C"
-msgstr "kur"
+msgstr "kmr"
 
 #: src/libvlc.c:861
 msgid ""

po/ku.po

+kmr.po
\ No newline at end of file