more small docs work

and don't cache gaussnoise

TODO

@@ -1,3 +1,13 @@
+- try:
+
+	$ vipsthumbnail 360mp.png --vips-leak --vips-concurrency=1
+	--vips-progress
+
+
+  works in tiles ... should it be strips?
+
+  no %complete feedback
+
 - why don't we get gtk-doc expansions in the leading chapters? we turn them on
 
 - need a thing to test C++ overloads 

doc/reference/using-python.xml

@@ -186,7 +186,8 @@ min_value, x_pos, y_pos = im.min(x = True, y = True)
           <para>
             It does a couple of more ambitious conversions. If an operation 
             takes several input images, you can use a constant for all but 
-            one of them and the wrapper will make a constant image for you.
+            one of them and the wrapper will make a constant image for you. 
+            For example, <code>.bandjoin()</code> 
           </para>
         </listitem>
       </itemizedlist>

libvips/create/gaussnoise.c

@@ -146,6 +146,7 @@ vips_gaussnoise_class_init( VipsGaussnoiseClass *class )
 {
 	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
 	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
+	VipsOperationClass *operation_class = (VipsOperationClass *) class;
 
 	gobject_class->set_property = vips_object_set_property;
 	gobject_class->get_property = vips_object_get_property;
@@ -154,6 +155,10 @@ vips_gaussnoise_class_init( VipsGaussnoiseClass *class )
 	vobject_class->description = _( "make a gaussnoise image" );
 	vobject_class->build = vips_gaussnoise_build;
 
+	/* We want a new set of numbers each time.
+	 */
+	operation_class->flags |= VIPS_OPERATION_NOCACHE;
+
 	VIPS_ARG_INT( class, "width", 4, 
 		_( "Width" ), 
 		_( "Image width in pixels" ),