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/load.c

@@ -36,6 +36,7 @@
 
 #include "wraster.h"
 #include "imgformat.h"
+#include "wr_i18n.h"
 
 
 typedef struct RCachedImage {