WebGLProgram: Use displacementMap only when the system supports vertex textures.

src/renderers/webgl/WebGLProgram.js

@@ -201,7 +201,7 @@ THREE.WebGLProgram = ( function () {
 				parameters.emissiveMap ? '#define USE_EMISSIVEMAP' : '',
 				parameters.bumpMap ? '#define USE_BUMPMAP' : '',
 				parameters.normalMap ? '#define USE_NORMALMAP' : '',
-				parameters.displacementMap ? '#define USE_DISPLACEMENTMAP' : '',
+				parameters.displacementMap && parameters.supportsVertexTextures ? '#define USE_DISPLACEMENTMAP' : '',
 				parameters.specularMap ? '#define USE_SPECULARMAP' : '',
 				parameters.alphaMap ? '#define USE_ALPHAMAP' : '',
 				parameters.vertexColors ? '#define USE_COLOR' : '',