src: remove forwards for v8::GC*logueCallback

These types are no longer used in the file and V8 4.9 no longer defines these
types anymore.

PR-URL: https://github.com/nodejs/node/pull/4381
Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>

src/node_counters.cc

@@ -11,8 +11,6 @@ namespace node {
 using v8::FunctionCallbackInfo;
 using v8::FunctionTemplate;
 using v8::GCCallbackFlags;
-using v8::GCEpilogueCallback;
-using v8::GCPrologueCallback;
 using v8::GCType;
 using v8::HandleScope;
 using v8::Isolate;

src/node_dtrace.cc

@@ -34,8 +34,6 @@ namespace node {
 using v8::FunctionCallbackInfo;
 using v8::FunctionTemplate;
 using v8::GCCallbackFlags;
-using v8::GCEpilogueCallback;
-using v8::GCPrologueCallback;
 using v8::GCType;
 using v8::HandleScope;
 using v8::Isolate;

src/node_lttng.cc

@@ -29,8 +29,6 @@ namespace node {
 using v8::FunctionCallbackInfo;
 using v8::FunctionTemplate;
 using v8::GCCallbackFlags;
-using v8::GCEpilogueCallback;
-using v8::GCPrologueCallback;
 using v8::GCType;
 using v8::HandleScope;
 using v8::Isolate;