src: export the ParseEncoding function on Windows

Makes the ParseEncoding symbol visible to addons on Windows.
It was already visible on Unices.

PR-URL: nodejs#1596
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

src/node.h

@@ -265,9 +265,10 @@ inline void NODE_SET_PROTOTYPE_METHOD(v8::Handle<v8::FunctionTemplate> recv,
 #define NODE_SET_PROTOTYPE_METHOD node::NODE_SET_PROTOTYPE_METHOD
 
 enum encoding {ASCII, UTF8, BASE64, UCS2, BINARY, HEX, BUFFER};
-enum encoding ParseEncoding(v8::Isolate* isolate,
-                            v8::Handle<v8::Value> encoding_v,
-                            enum encoding default_encoding = BINARY);
+NODE_EXTERN enum encoding ParseEncoding(
+    v8::Isolate* isolate,
+    v8::Handle<v8::Value> encoding_v,
+    enum encoding default_encoding = BINARY);
 NODE_DEPRECATED("Use ParseEncoding(isolate, ...)",
                 inline enum encoding ParseEncoding(
       v8::Handle<v8::Value> encoding_v,