ox: Convert Japanese translation from utf-8 to default

* lisp/ox.el (org-export-dictionary): Convert all Japanese translation
  from utf-8 to default.

There shouldn't be much need for exporters and users to worry about
the coding system of the final output.  If one wants to export a
"Japanese" document, he should already have the document with Japanese
capable coding system. In that case, Emacs should be able to handle
the coding system conversion form the translation table to the
designated file coding system.

There are two cases which I can think don't work:

  - all words in the document are written in romaji, and one wants
    romaji translations

  - the documents are writ en in a language which does not support
    Japanese character set, ie English or French, and one wants to use
    Japanese for non-content strings, ie TOC.

These cases are too rare that we can ignore for now.

lisp/ox.el

@@ -5331,7 +5331,7 @@ them."
      ("hu" :default "Szerzõ")
      ("is" :html "Höfundur")
      ("it" :default "Autore")
-     ("ja" :html "著者" :utf-8 "著者")
+     ("ja" :default "著者" :html "著者")
      ("nl" :default "Auteur")
      ("no" :default "Forfatter")
      ("nb" :default "Forfatter")
@@ -5347,7 +5347,7 @@ them."
      ("es" :default "Continúa de la página anterior")
      ("fr" :default "Suite de la page précédente")
      ("it" :default "Continua da pagina precedente")
-     ("ja" :utf-8 "前ページからの続き")
+     ("ja" :default "前ページからの続き")
      ("nl" :default "Vervolg van vorige pagina")
      ("pt" :default "Continuação da página anterior")
      ("ru" :html "(Продолжение)"
@@ -5357,7 +5357,7 @@ them."
      ("es" :default "Continúa en la siguiente página")
      ("fr" :default "Suite page suivante")
      ("it" :default "Continua alla pagina successiva")
-     ("ja" :utf-8 "次ページに続く")
+     ("ja" :default "次ページに続く")
      ("nl" :default "Vervolg op volgende pagina")
      ("pt" :default "Continua na página seguinte")
      ("ru" :html "(Продолжение следует)"
@@ -5374,7 +5374,7 @@ them."
      ("hu" :html "Dátum")
      ("is" :default "Dagsetning")
      ("it" :default "Data")
-     ("ja" :html "日付" :utf-8 "日付")
+     ("ja" :default "日付" :html "日付")
      ("nl" :default "Datum")
      ("no" :default "Dato")
      ("nb" :default "Dato")
@@ -5403,7 +5403,7 @@ them."
      ("de" :default "Abbildung")
      ("es" :default "Figura")
      ("et" :default "Joonis")
-     ("ja" :html "図" :utf-8 "図")
+     ("ja" :default "図" :html "図")
      ("no" :default "Illustrasjon")
      ("nb" :default "Illustrasjon")
      ("nn" :default "Illustrasjon")
@@ -5416,7 +5416,7 @@ them."
      ("es" :default "Figura %d:")
      ("et" :default "Joonis %d:")
      ("fr" :default "Figure %d :" :html "Figure %d :")
-     ("ja" :html "図%d: " :utf-8 "図%d: ")
+     ("ja" :default "図%d: " :html "図%d: ")
      ("no" :default "Illustrasjon %d")
      ("nb" :default "Illustrasjon %d")
      ("nn" :default "Illustrasjon %d")
@@ -5436,7 +5436,7 @@ them."
      ("hu" :html "Lábjegyzet")
      ("is" :html "Aftanmálsgreinar")
      ("it" :html "Note a piè di pagina")
-     ("ja" :html "脚注" :utf-8 "脚注")
+     ("ja" :default "脚注" :html "脚注")
      ("nl" :default "Voetnoten")
      ("no" :default "Fotnoter")
      ("nb" :default "Fotnoter")
@@ -5497,7 +5497,7 @@ them."
      ("es" :default "Tabla")
      ("et" :default "Tabel")
      ("fr" :default "Tableau")
-     ("ja" :html "表" :utf-8 "表")
+     ("ja" :default "表" :html "表")
      ("ru" :html "Таблица" :utf-8 "Таблица")
      ("zh-CN" :html "表" :utf-8 "表"))
     ("Table %d:"
@@ -5506,7 +5506,7 @@ them."
      ("es" :default "Tabla %d")
      ("et" :default "Tabel %d")
      ("fr" :default "Tableau %d :")
-     ("ja" :html "表%d:" :utf-8 "表%d:")
+     ("ja" :default "表%d:" :html "表%d:")
      ("no" :default "Tabell %d")
      ("nb" :default "Tabell %d")
      ("nn" :default "Tabell %d")
@@ -5527,7 +5527,7 @@ them."
      ("hu" :html "Tartalomjegyzék")
      ("is" :default "Efnisyfirlit")
      ("it" :default "Indice")
-     ("ja" :html "目次" :utf-8 "目次")
+     ("ja" :default "目次" :html "目次")
      ("nl" :default "Inhoudsopgave")
      ("no" :default "Innhold")
      ("nb" :default "Innhold")