Platform: add tests for setMin/MaxWindowSize().

DPI scaling is not respected and viewport event is not fired on SDL.
Ugh.

src/Magnum/Platform/Test/GlfwApplicationTest.cpp

@@ -61,7 +61,14 @@ struct GlfwApplicationTest: Platform::Application {
         } else if(event.key() == KeyEvent::Key::T) {
             Debug{} << "setting window title";
             setWindowTitle("This is a UTF-8 Window Title™!");
-        } else if(event.key() == KeyEvent::Key::H) {
+        }
+        #if GLFW_VERSION_MAJOR*100 + GLFW_VERSION_MINOR >= 302
+        else if(event.key() == KeyEvent::Key::W) {
+            Debug{} << "setting max window size, which should trigger a viewport event if the size changes";
+            setMaxWindowSize(Vector2i{700, 500});
+        }
+        #endif
+        else if(event.key() == KeyEvent::Key::H) {
             Debug{} << "toggling hand cursor";
             setCursor(cursor() == Cursor::Arrow ? Cursor::Hand : Cursor::Arrow);
         } else if(event.key() == KeyEvent::Key::L) {

src/Magnum/Platform/Test/Sdl2ApplicationTest.cpp

@@ -86,7 +86,14 @@ struct Sdl2ApplicationTest: Platform::Application {
         } else if(event.key() == KeyEvent::Key::T) {
             Debug{} << "setting window title";
             setWindowTitle("This is a UTF-8 Window Title™!");
-        } else if(event.key() == KeyEvent::Key::H) {
+        }
+        #ifndef CORRADE_TARGET_EMSCRIPTEN
+        else if(event.key() == KeyEvent::Key::W) {
+            Debug{} << "setting max window size, which should trigger a viewport event";
+            setMaxWindowSize(Vector2i{700, 500});
+        }
+        #endif
+        else if(event.key() == KeyEvent::Key::H) {
             Debug{} << "toggling hand cursor";
             setCursor(cursor() == Cursor::Arrow ? Cursor::Hand : Cursor::Arrow);
         }