Misc changes for .18

* app/indexed_palette.c: fix for wrong color selected in indexed
        palette dialog

        * app/xcf.c: don't crash on bad input (0 byte files)

        * app/plug_in.h
        * app/plug_in.c: fixes Gimp's most obscure bug. Failed plugin
        queries are handle correctly now

        * app/commands.c: added marching ants speed to preferences

        * plug-ins/tiff/tiff.c: correction for inversion for MINISWHITE
        images without alpha

        * plug-ins/pcx/pcx.c: updated to new version

        * app/paint_funcs.h: changed OPAQUE and TRANSPARENT to
        OPAQUE_OPACITY and TRANSPARENT_OPACITY to avoid possible
        conflicts. All affects .c files changed.

-Yosh

app/convolve.c

@@ -326,7 +326,7 @@ convolve_motion (PaintCore *paint_core,
     }
 
   /*  paste the newly painted canvas to the gimage which is being worked on  */
-  paint_core_replace_canvas (paint_core, drawable, OPAQUE,
+  paint_core_replace_canvas (paint_core, drawable, OPAQUE_OPACITY,
 			   (int) (get_brush_opacity () * 255),
 			   SOFT, INCREMENTAL);
 }