WRaster: add functions to save image on disk

This patch adds the RSaveTitledImage() function to the WRaster lib
to be able to save file on disk either as a PNG or a JPEG file.
Those two formats depends on optional external libs.
The function can take an optional title/comment which will
be save inside the file.

The WRaster lib and header versions are bumped.

wrlib/imgformat.h

@@ -29,7 +29,6 @@
 #ifndef IMGFORMAT_INTERNAL_H
 #define IMGFORMAT_INTERNAL_H
 
-
 typedef enum {
 	IM_ERROR   = -1,
 	IM_UNKNOWN =  0,
@@ -82,8 +81,15 @@ void RReleaseMagick(void);
 /*
  * Function for Saving in a specific format
  */
-Bool RSaveXPM(RImage *image, const char *file);
+Bool RSaveXPM(RImage *image, const char *filename);
 
+#ifdef USE_PNG
+Bool RSavePNG(RImage *image, const char *filename, char *title);
+#endif
+
+#ifdef USE_JPEG
+Bool RSaveJPEG(RImage *image, const char *filename, char *title);
+#endif
 
 /*
  * Function to terminate properly