Fix #3387: Safebooru: Two tag searches fail for members.

Makes the `rating:s` and `-status:deleted` tags not count against the
tag limit.

config/danbooru_default_config.rb

@@ -169,6 +169,11 @@ module Danbooru
       end
     end
 
+    # Return true if the given tag shouldn't count against the user's tag search limit.
+    def is_unlimited_tag?(tag)
+      !!(tag =~ /\A(-?status:deleted|rating:s.*|limit:.+)\z/i)
+    end
+
     # After this many pages, the paginator will switch to sequential mode.
     def max_numbered_pages
       1_000