Item7166: TOC variable has potential infinite recursion

TWikibug:Item6864 expands variables when handling %TOC%, but this exposes potential infinite recursion possibility.
To reproduce it, just create two pages, "TestPage1" and "TestPage2". These two pages have exactly the same content as

%TOC{TestPage1}%
%TOC{TestPage2}%
---++ %TOPIC%
---++ %WEB%

Then neither "TestPage1" nor "TestPage2" can be opened until timeout.

I escape TOC variables before TOC handler expands variables again.

$ svn diff TWiki.pm
Index: TWiki.pm
===================================================================
--- TWiki.pm    (revision 25187)
+++ TWiki.pm    (working copy)
@@ -2599,7 +2599,8 @@
         }
         my $meta;
         ( $meta, $text ) = $this->{store}->readTopic( $this->{user}, $web, $topic );
-
+        # Item7166: Escape %TOC% to avoid infinite recursion.
+        $text =~ s/%(TOC[{%])/%<nop>$1/g;
         # Item6864: 2012-03-29 TWiki:Main.GertjanVanOosten, gertjan at west dot nl:
         #   Handle common tags, as the text may contain variables etc. that need
         #   to be expanded before generating the TOC for another topic.
         $text = $this->handleCommonTags( $text, $web, $topic, $meta );

-- TWiki:Main/YaojunFei - 2013-02-26

This is now fixed differently in Item7286. There was still an infinite loop possible if an INCLUDEd topic had a TOC.

-- TWiki:Main.PeterThoeny - 2013-06-28