Fix austrian language code

(cherry picked from commit b12ea3b731)

lib/languages

@@ -224,6 +224,7 @@ End
 
 # In polyglossia, this is supported since release 1.33.4 (May 2014)
 # We introduce it with LyX 2.2 to give the support time to settle.
+# Due to the variety, we use no country code.
 Language austrian
 	GuiName          "German (Austria, old spelling)"
 	BabelName        austrian
@@ -231,7 +232,8 @@ Language austrian
 	PolyglossiaOpts  "variant=austrian,spelling=old,babelshorthands=true"
 	QuoteStyle       german
 	Encoding         iso8859-15
-	LangCode         de_AT
+	LangCode         de
+	LangVariety      alt
 End
 
 # In polyglossia, this is supported since release 1.33.4 (May 2014)

status.23x

@@ -285,6 +285,8 @@ What's new
 - Fix bug that TeX files were not detected when reconfiguring LyX 
   (bug 11053).
 
+- Fix language code of Austrian (old spelling).
+
 
 * DOCUMENTATION AND LOCALIZATION