posts: fix missing pages for members using hide_deleted_posts option.

Bug: If a Member had the hide_deleted_posts option turned on and did a
two tag search, no pages would show up.

Cause: The hide_deleted_posts option implicitly adds the -status:deleted
tag, but this tag wasn't considered a free metatag, so this caused
Post.fast_count to fail and return zero because the search was treated
as a three tag search.

ref: https://danbooru.donmai.us/forum_topics/16829

config/danbooru_default_config.rb

@@ -109,7 +109,7 @@ module Danbooru
 
     # Return true if the given tag shouldn't count against the user's tag search limit.
     def is_unlimited_tag?(term)
-      term.type == :metatag && term.name.in?(%w[status rating limit])
+      term.type == :metatag && term.name.in?(%w[-status status rating limit])
     end
 
     # After this many pages, the paginator will switch to sequential mode.

test/unit/post_test.rb

@@ -1983,6 +1983,13 @@ class PostTest < ActiveSupport::TestCase
           Cache.expects(:put).with(Post.count_cache_key("aaa score:42"), 1, 180)
           Post.fast_count("aaa score:42")
         end
+
+        should "work with the hide_deleted_posts option turned on" do
+          user = create(:user, hide_deleted_posts: true)
+          as(user) do
+            assert_equal(1, Post.fast_count("aaa score:42"))
+          end
+        end
       end
 
       context "a blank search" do