* Sets a native filter. This must be first set in plugin_natives(), but future calls will
* simply set a new filter.
* This filter will allow your plugin to load even if its modules aren't loaded. For example,
* if Fun isn't loaded and you use set_user_frags, your plugin will still load. However, if you
* attempt to call this native, your filter will intercept it with these parameters:
* public function native_filter(const name, index)
* native - name of native
* index - index of native
* trap - 0 if native couldn't be found, 1 if native use was attempted
* If you return PLUGIN_HANDLED, no error is thrown. If you return PLUGIN_CONTINUE,
* your plugin will have a run-time-error. To print your own error, or change the default,
* you can return PLUGIN_HANDLED or return PLUGIN_CONTINUE and use set_error_filter.
* If you return PLUGIN_CONTINUE when trap is 0, the plugin will ABORT AND FAIL TO LOAD!
* When trap is 0, it is unsafe to use natives that modify the server or use other plugins.
native set_native_filter(const handler);