Don't use deprecated functionality.

src/MagnumPlugins/AnyAudioImporter/AnyImporter.cpp

@@ -68,7 +68,7 @@ void AnyImporter::doOpenFile(const std::string& filename) {
 
     /* Try to open the file (error output should be printed by the plugin
        itself) */
-    std::unique_ptr<AbstractImporter> importer = static_cast<PluginManager::Manager<AbstractImporter>*>(manager())->instance(plugin);
+    std::unique_ptr<AbstractImporter> importer = static_cast<PluginManager::Manager<AbstractImporter>*>(manager())->instantiate(plugin);
     if(!importer->openFile(filename)) return;
 
     /* Success, save the instance */

src/MagnumPlugins/AnyImageConverter/AnyImageConverter.cpp

@@ -73,7 +73,7 @@ bool AnyImageConverter::doExportToFile(const ImageView2D& image, const std::stri
 
     /* Try to convert the file (error output should be printed by the plugin
        itself) */
-    return static_cast<PluginManager::Manager<AbstractImageConverter>*>(manager())->instance(plugin)->exportToFile(image, filename);
+    return static_cast<PluginManager::Manager<AbstractImageConverter>*>(manager())->instantiate(plugin)->exportToFile(image, filename);
 }
 
 bool AnyImageConverter::doExportToFile(const CompressedImageView2D&, const std::string& filename) {

src/MagnumPlugins/AnyImageImporter/AnyImageImporter.cpp

@@ -111,7 +111,7 @@ void AnyImageImporter::doOpenFile(const std::string& filename) {
 
     /* Try to open the file (error output should be printed by the plugin
        itself) */
-    std::unique_ptr<AbstractImporter> importer = static_cast<PluginManager::Manager<AbstractImporter>*>(manager())->instance(plugin);
+    std::unique_ptr<AbstractImporter> importer = static_cast<PluginManager::Manager<AbstractImporter>*>(manager())->instantiate(plugin);
     if(!importer->openFile(filename)) return;
 
     /* Success, save the instance */

src/MagnumPlugins/AnySceneImporter/AnySceneImporter.cpp

@@ -128,7 +128,7 @@ void AnySceneImporter::doOpenFile(const std::string& filename) {
 
     /* Try to open the file (error output should be printed by the plugin
        itself) */
-    std::unique_ptr<AbstractImporter> importer = static_cast<PluginManager::Manager<AbstractImporter>*>(manager())->instance(plugin);
+    std::unique_ptr<AbstractImporter> importer = static_cast<PluginManager::Manager<AbstractImporter>*>(manager())->instantiate(plugin);
     if(!importer->openFile(filename)) return;
 
     /* Success, save the instance */