Added missing 'used but not declared' heightMax property.

src/extras/controls/FirstPersonControls.js

@@ -24,6 +24,7 @@ THREE.FirstPersonControls = function ( object, domElement ) {
 	this.heightSpeed = false;
 	this.heightCoef = 1.0;
 	this.heightMin = 0.0;
+	this.heightMax = 1.0;
 
 	this.constrainVertical = false;
 	this.verticalMin = 0;