GtkApplication: Call setlocale early

If we don't call setlocale early enough,
--help output may come out misformatted.

Fixes: #4234

gtk/gtkapplication.c

@@ -294,6 +294,9 @@ gtk_application_local_command_line (GApplication   *application,
                                     char         ***arguments,
                                     int            *exit_status)
 {
+  /* We need to call setlocale() here so --help output works */
+  setlocale_initialization ();
+
   return G_APPLICATION_CLASS (gtk_application_parent_class)->local_command_line (application, arguments, exit_status);
 }
 

gtk/gtkmain.c

@@ -362,7 +362,7 @@ enum_locale_proc (LPTSTR locale)
   
 #endif
 
-static void
+void
 setlocale_initialization (void)
 {
   static gboolean initialized = FALSE;

gtk/gtkprivate.h

@@ -150,6 +150,8 @@ GBytes *get_emoji_data (void);
 
 char * _gtk_elide_underscores (const char *original);
 
+void setlocale_initialization (void);
+
 G_END_DECLS
 
 #endif /* __GTK_PRIVATE_H__ */