add im_tile_cache() to vips7 op db

try using this from nip2 instead of im_cache()

im_cache() uses vips_sink_screen() and is probably quite a bit slower

TODO

@@ -1,12 +1,28 @@
 
 - can we use postbuild elsewhere? look at use of "preclose" / "written", etc. 
 
+
+
+
 - why is cache in nip2 so slow? its awful
 
   investigate again
 
   is it using vips_sinkscreen()? should it use tilecache?
 
+  Cache calls cache in _stdenv.def
+
+  cache calls im_cache()
+
+  im_cache() calls vips_sink_screen()
+
+
+ 
+  im_tile_cache() calls vips_tilecache() 
+
+  add im_tile_cache to vips7 op db, try using it from nip2
+
+
 
 - test draw_mask on labq images
 

libvips/deprecated/package.c

@@ -497,6 +497,30 @@ static im_function cache_desc = {
 	cache_args 			/* Arg list */
 };
 
+/* Call im_tile_cache() via arg vector.
+ */
+static int
+tile_cache_vec( im_object *argv )
+{
+	int tile_width = *((int *) argv[2]);
+	int tile_height = *((int *) argv[3]);
+	int max_tiles = *((int *) argv[4]);
+
+	return( im_tile_cache( argv[0], argv[1], 
+		tile_width, tile_height, max_tiles ) );
+}
+
+/* Description of im_cache.
+ */ 
+static im_function tile_cache_desc = {
+	"im_tile_cache", 		/* Name */
+	"cache results of an operation",/* Description */
+	0,				/* Flags */
+	tile_cache_vec, 		/* Dispatch function */
+	VIPS_NUMBER( cache_args ), 	/* Size of arg list */
+	cache_args 			/* Arg list */
+};
+
 /* im_binfile() args.
  */
 static im_arg_desc binfile_args[] = {
@@ -546,6 +570,7 @@ static im_function binfile_desc = {
 static im_function *iofuncs_list[] = {
 	&binfile_desc,
 	&cache_desc,
+	&tile_cache_desc,
 	&concurrency_get_desc,
 	&getext_desc,
 	&guess_prefix_desc,