child_process: move binding init in constructor

Doing this in net.Socket constructor has much more overhead, and
error is actually may happen before the construction of socket object.

lib/child_process.js

@@ -668,6 +668,10 @@ function maybeClose(subprocess) {
 function ChildProcess() {
   EventEmitter.call(this);
 
+  // Initialize TCPWrap and PipeWrap
+  process.binding('tcp_wrap');
+  process.binding('pipe_wrap');
+
   var self = this;
 
   this._closesNeeded = 1;

lib/net.js

@@ -142,10 +142,6 @@ function Socket(options) {
   stream.Duplex.call(this, options);
 
   if (options.handle) {
-    // Initialize TCPWrap and PipeWrap
-    process.binding('tcp_wrap');
-    process.binding('pipe_wrap');
-
     this._handle = options.handle; // private
   } else if (typeof options.fd !== 'undefined') {
     this._handle = createPipe();