src: add node::FreeEnvironment public API

Since debugger::Agent's interface is not exported, third party embedders
will have linking errors if they call Environment's destructor directly.

PR-URL: https://github.com/nodejs/node/pull/3098
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/node.cc

@@ -3386,6 +3386,13 @@ void LoadEnvironment(Environment* env) {
   f->Call(Null(env->isolate()), 1, &arg);
 }
 
+
+void FreeEnvironment(Environment* env) {
+  CHECK_NE(env, nullptr);
+  env->Dispose();
+}
+
+
 static void PrintHelp();
 
 static bool ParseDebugOpt(const char* arg) {

src/node.h

@@ -200,6 +200,7 @@ NODE_EXTERN Environment* CreateEnvironment(v8::Isolate* isolate,
                                            int exec_argc,
                                            const char* const* exec_argv);
 NODE_EXTERN void LoadEnvironment(Environment* env);
+NODE_EXTERN void FreeEnvironment(Environment* env);
 
 // NOTE: Calling this is the same as calling
 // CreateEnvironment() + LoadEnvironment() from above.