Add DEFINED TAGS listing to <dump> output

Custom <tag name=...> definitions have no scope levels the way variables
do - __tag.cpp always registers into the single global.tags map regardless
of where in the script the definition sits, so this is one flat list, not
broken out by global/local/parent like the existing variable/keyword
sections. Verified end-to-end via a real jet-2.0 run: two tags defined
before <dump> both appear correctly in the DEFINED TAGS section.

__dump.cpp

@@ -33,6 +33,15 @@ namespace jet {
       for (auto i = global.cookies.data.begin(); i != global.cookies.data.end(); i++)
 	outFile << i->first << "=[" << i->second << "]" << std::endl;
 
+      // Unlike variables (which have real global/local/parent scoping),
+      // custom <tag name="..."> definitions have only one level - __tag.cpp
+      // always registers into global.tags regardless of where in the
+      // script the definition sits, so there's nothing to break out by
+      // scope here.
+      outFile << "*** DEFINED TAGS ***" << std::endl;
+      for (auto i = global.tags.begin(); i != global.tags.end(); i++)
+	outFile << i->first << std::endl;
+
       outFile.close();
       
    }