allow .dz as a destination

so this now works:

$ vips extract_area 50310.svs x.dz 10 10 100 100

and writes a deepzoom pyramid

ChangeLog

@@ -20,6 +20,8 @@
 - tiff reader allows separate planes for strip read
 - tiff reader allows many more formats, eg. 32-bit int, complex, etc. 
 - added vips_image_new_matrixv()
+- dzsave basename param now called filename, so you can use .dz as a
+  destination (basename is still there but deprecated)
 
 3/7/13 started 7.34.2
 - lower priority for Matlab load to reduce segvs from Mat_Open(), thanks

libvips/foreign/dzsave.c

@@ -1399,9 +1399,9 @@ vips_foreign_save_dz_class_init( VipsForeignSaveDzClass *class )
 	save_class->format_table = bandfmt_dz;
 	save_class->coding[VIPS_CODING_LABQ] = TRUE;
 
-	VIPS_ARG_STRING( class, "basename", 1, 
-		_( "Base name" ),
-		_( "Base name to save to" ),
+	VIPS_ARG_STRING( class, "filename", 1, 
+		_( "Filename" ),
+		_( "Filename to save to" ),
 		VIPS_ARGUMENT_REQUIRED_INPUT, 
 		G_STRUCT_OFFSET( VipsForeignSaveDz, basename ),
 		NULL );
@@ -1474,6 +1474,13 @@ vips_foreign_save_dz_class_init( VipsForeignSaveDzClass *class )
 		G_STRUCT_OFFSET( VipsForeignSaveDz, basename ),
 		NULL );
 
+	VIPS_ARG_STRING( class, "basename", 1, 
+		_( "Base name" ),
+		_( "Base name to save to" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT | VIPS_ARGUMENT_DEPRECATED, 
+		G_STRUCT_OFFSET( VipsForeignSaveDz, basename ),
+		NULL );
+
 	VIPS_ARG_INT( class, "tile_width", 12, 
 		_( "Tile width" ), 
 		_( "Tile width in pixels" ),