lang: merge Japanese progress from master

lang/Makefile

@@ -7,7 +7,7 @@ MSGFMT=		${_MSGFMT} --strict
 
 LOCALEDIR=	/usr/local/share/locale/%%LANG%%/LC_MESSAGES
 
-LANGUAGES=	de_DE zh_CN
+LANGUAGES=	de_DE ja_JP zh_CN
 TEMPLATE=	en_US
 INSTALL=
 PLIST=

src/www/system_general.php

@@ -43,6 +43,7 @@ function get_locale_list()
 	$locales['en_US'] = gettext('English');
 	$locales['zh_CN'] = gettext('Chinese (Simplified)');
 	$locales['de_DE'] = gettext('German');
+	$locales['ja_JP'] = gettext('Japanese');
 
 	return $locales;
 }