Minor documentation fixes.

It's not needed to have empty `()` after class name in this type
of expressions:

    (new Object())
        ->setFoo(a)
        ->setBar(b);

doc/debug-tools.dox

@@ -63,7 +63,7 @@ SceneGraph::DrawableGroup3D debugDrawables;
 
 // Create renderer options which will be referenced later by "my" resource key
 DebugTools::ResourceManager::instance()->set("my",
-    (new DebugTools::ObjectRendererOptions())->setSize(0.3f));
+    (new DebugTools::ObjectRendererOptions)->setSize(0.3f));
 
 // Create debug renderer for given object, use "my" options for it. The
 // renderer is automatically added to the object features and also to

doc/platform.dox

@@ -147,7 +147,7 @@ window size 800x600 pixels). If you want something else, you can pass
 constructor. Using method chaining it can be done conveniently like this:
 @code
 MyApplication::MyApplication(int& argc, char** argv):
-    Platform::GlutApplication(argc, argv, (new Configuration())
+    Platform::GlutApplication(argc, argv, (new Configuration)
         ->setTitle("My Application")->setSize({800, 600}) {
     // ...
 }
@@ -161,7 +161,7 @@ instead of Configuration instance and then specify it later with
 MyApplication::MyApplication(int& argc, char** argv): Platform::GlutApplication(argc, argv, nullptr) {
     // ...
 
-    createContext((new Configuration())
+    createContext((new Configuration)
         ->setTitle("My Application")
         ->setSize(size));
 

src/DebugTools/ForceRenderer.h

@@ -90,9 +90,8 @@ See @ref debug-tools-renderers for more information.
 Example code:
 @code
 // Create some options
-DebugTools::ResourceManager::instance()->set("my", (new DebugTools::ForceRendererOptions()
+DebugTools::ResourceManager::instance()->set("my", (new DebugTools::ForceRendererOptions)
-    ->setScale(5.0f)
+    ->setScale(5.0f)->setColor(Color3<>::fromHSV(120.0_degf, 1.0f, 0.7f)));
-    ->setColor(Color3<>::fromHSV(120.0_degf, 1.0f, 0.7f)));
 
 // Create debug renderer for given object, use "my" options for it
 Object3D* object;

src/DebugTools/ObjectRenderer.h

@@ -74,8 +74,8 @@ Visualizes object position, rotation and scale using colored axes. See
 Example code:
 @code
 // Create some options
-DebugTools::ResourceManager::instance()->set("my",
+DebugTools::ResourceManager::instance()->set("my", (new DebugTools::ObjectRendererOptions)
-    (new DebugTools::ObjectRendererOptions())->setSize(0.3f));
+    ->setSize(0.3f));
 
 // Create debug renderer for given object, use "my" options for it
 Object3D* object;

src/DebugTools/ShapeRenderer.h

@@ -104,8 +104,8 @@ Visualizes collision shapes using wireframe primitives. See
 Example code:
 @code
 // Create some options
-DebugTools::ResourceManager::instance()->set("red",
+DebugTools::ResourceManager::instance()->set("red", (new DebugTools::ShapeRendererOptions)
-    (new DebugTools::ShapeRendererOptions())->setColor({1.0f, 0.0f, 0.0f}));
+    ->setColor({1.0f, 0.0f, 0.0f}));
 
 // Create debug renderer for given shape, use "red" options for it
 Physics::ObjectShape2D* shape;