- We do not need the return type. If a plugin declares it can handle the
packet it should do so. We don't have any fallback logic in place and
the packet types are namespaced with the plugin IDs anyway.
- Provide a default implementation with a warning, not all plugins need
to overwrite this
This is not needed, because only a symbol to create the KPluginFactory
instance must be exported. The KPluginFactory macros or rather the underlying
Q_PLUGIN_METADATA macro already take care of that.
In other plugin code of KDE, we also do not export classes.
The size of the generated plugin files is nearly identical, but removing
the macros avoids confusion for developers.
