Adding "system default" (default locale) option for IDE language.

That is, if the editor.languages.current preference is empty (or
missing), use the default system locale.

Author: damellis

app/src/processing/app/I18n.java

@@ -25,7 +25,8 @@ public class I18n {
   static protected void init (String language) {
     // there might be a null pointer exception ... most likely will never happen but the jvm gets mad
     try {
-      locale = new Locale(language);
+      if (language == null || language.trim().isEmpty()) locale = Locale.getDefault();
+      else locale = new Locale(language);
       i18n = ResourceBundle.getBundle("processing.app.Resources", locale);
     } catch (java.lang.NullPointerException e) {
     }

app/src/processing/app/Preferences.java

@@ -112,6 +112,7 @@ public class Preferences {
 
   // language related arrays, please read notes later, where the language combo box is introduced
   String[] languages = {
+                        _("System Default"),
                         _("Catalan"),
                         _("Chinese Simplified"),
                         _("Chinese Taiwan"),
@@ -133,6 +134,7 @@ public class Preferences {
                         _("Russian"),
                         _("Spanish")};
   String[] languagesISO = {
+                        "",
                         "ca",
                         "zh_cn",
                         "zh_tw",