HPCC-8030 R/Java/JavaScript/Python language support in ECL

More changes in response to code review

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>

plugins/javaembed/javaembed.cpp

@@ -357,6 +357,7 @@ static __thread ThreadTermFunc threadHookChain;
 static void releaseContext()
 {
     delete threadContext;
+    threadContext = NULL;
     if (threadHookChain)
         (*threadHookChain)();
 }

plugins/v8embed/v8embed.cpp

@@ -191,7 +191,6 @@ class V8JavascriptEmbedContext : public CInterfaceOf<IEmbedContext>
 public:
     V8JavascriptEmbedContext()
     {
-        Link();  // Deliberately 'leak' in order to avoid freeing this global object
     }
     virtual IEmbedFunctionContext *createFunctionContext(bool isImport, const char *options)
     {