WebGLProgram: Fixed displacementMap bug.

src/renderers/webgl/WebGLPrograms.js

@@ -15,7 +15,7 @@ THREE.WebGLPrograms = function ( renderer, capabilities ) {
 
 	var parameterNames = [
 		"precision", "supportsVertexTextures", "map", "envMap", "envMapMode",
-		"lightMap", "aoMap", "emissiveMap", "bumpMap", "normalMap", "specularMap",
+		"lightMap", "aoMap", "emissiveMap", "bumpMap", "normalMap", "displacementMap", "specularMap",
 		"alphaMap", "combine", "vertexColors", "fog", "useFog", "fogExp",
 		"flatShading", "sizeAttenuation", "logarithmicDepthBuffer", "skinning",
 		"maxBones", "useVertexTexture", "morphTargets", "morphNormals",