Use process.hrtime() for Clock in node.js builds

As discussed in #2975.

utils/npm/header.js

@@ -1,3 +1,21 @@
 
 var window = window || {};
 var self = self || {};
+
+// High-resulution counter: emulate window.performance.now() for THREE.CLOCK
+if( window.performance === undefined ) {
+
+	window.performance = { };
+
+}
+
+if( window.performance.now === undefined ) {
+
+	window.performance.now = function () {
+
+		var time = process.hrtime();
+		return ( time[0] + time[1] / 1e9 ) * 1000;
+
+	};
+
+}