Fix font encoding with japanese

Since japanese omits fontencoding, the encoding of latin text in fact is OT1.

Candidate for branch, but I would welcome Koji's input.

lib/languages

@@ -573,6 +573,8 @@ End
 # japanese must be loaded locally with babel options,
 # not globally via class options
 # http://www.lyx.org/trac/ticket/4597#c4
+# Since japanese does not load fontenc, we set
+# Internalencoding to true.
 Language japanese
 	GuiName          "Japanese"
 	BabelName        japanese
@@ -580,6 +582,7 @@ Language japanese
 	LangCode         ja_JP
 	AsBabelOptions   true
 	Requires         japanese
+	InternalEncoding true
 End
 
 # uses CJK package