WRaster: Create header for i18n helper functions

This patch is just adding a single header, but because it also modifies
all the C files to add the #include, it was made as a patch on its own to
ease review.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

wrlib/wr_i18n.h

@@ -0,0 +1,41 @@
+/*
+ *  Window Maker window manager
+ *
+ *  Copyright (c) 2021 Window Maker Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program, see the file COPYING.
+ */
+
+/*
+ * This file defines the basic stuff for WRaster's message
+ * internationalization in the code
+ */
+
+#ifndef WRASTER_I18N_H
+#define WRASTER_I18N_H
+
+#if defined(HAVE_LIBINTL_H) && defined(I18N)
+# include <libintl.h>
+# define _(text) dgettext("WRaster", (text))
+#else
+# define _(text) (text)
+#endif
+
+/*
+ * the N_ macro is used for initializers, it will make xgettext pick the
+ * string for translation when generating PO files
+ */
+#define N_(text) (text)
+
+#endif