Stress how Array instances returned from plugins should look like.

src/Magnum/Audio/AbstractImporter.h

@@ -61,6 +61,11 @@ checked by the implementation:
     there is any file opened.
 
 Plugin interface string is `"cz.mosra.magnum.Audio.AbstractImporter/0.1"`.
+
+@attention @ref Containers::Array instances returned from the plugin should
+    *not* use anything else than the default deleter, otherwise this can cause
+    dangling function pointer call on array destruction if the plugin gets
+    unloaded before the array is destroyed.
 */
 class MAGNUM_AUDIO_EXPORT AbstractImporter: public PluginManager::AbstractManagingPlugin<AbstractImporter> {
     CORRADE_PLUGIN_INTERFACE("cz.mosra.magnum.Audio.AbstractImporter/0.1")

src/Magnum/Text/AbstractFontConverter.h

@@ -69,6 +69,11 @@ checked by the implementation:
     array passed.
 
 Plugin interface string is `"cz.mosra.magnum.Text.AbstractFontConverter/0.1.2"`.
+
+@attention @ref Containers::Array instances returned from the plugin should
+    *not* use anything else than the default deleter, otherwise this can cause
+    dangling function pointer call on array destruction if the plugin gets
+    unloaded before the array is destroyed.
 */
 class MAGNUM_TEXT_EXPORT AbstractFontConverter: public PluginManager::AbstractPlugin {
     CORRADE_PLUGIN_INTERFACE("cz.mosra.magnum.Text.AbstractFontConverter/0.1.2")

src/Magnum/Trade/AbstractImageConverter.h

@@ -63,6 +63,11 @@ checked by the implementation:
     if @ref Feature::ConvertCompressedData is supported.
 
 Plugin interface string is `"cz.mosra.magnum.Trade.AbstractImageConverter/0.2.1"`.
+
+@attention @ref Containers::Array instances returned from the plugin should
+    *not* use anything else than the default deleter, otherwise this can cause
+    dangling function pointer call on array destruction if the plugin gets
+    unloaded before the array is destroyed.
 */
 class MAGNUM_EXPORT AbstractImageConverter: public PluginManager::AbstractManagingPlugin<AbstractImageConverter> {
     CORRADE_PLUGIN_INTERFACE("cz.mosra.magnum.Trade.AbstractImageConverter/0.2.1")

src/Magnum/Trade/AbstractImporter.h

@@ -74,6 +74,11 @@ checked by the implementation:
 
 Plugin interface string is `"cz.mosra.magnum.Trade.AbstractImporter/0.3"`.
 
+@attention @ref Containers::Array instances returned from the plugin should
+    *not* use anything else than the default deleter, otherwise this can cause
+    dangling function pointer call on array destruction if the plugin gets
+    unloaded before the array is destroyed.
+
 @todo How to handle casting from std::unique_ptr<> in more convenient way?
 */
 class MAGNUM_EXPORT AbstractImporter: public PluginManager::AbstractManagingPlugin<AbstractImporter> {