doc: clarify which plugins get a global keyset handle
*
* @par Global KeySet Handle
*
- * Plugins in a backend will get a handle to a global keyset.
+ * Global plugins and plugins in a backend will get a handle to a global keyset.
* This allows them to exchange information with other plugins.
* The global keyset is tied to a KDB handle, initialized on kdbOpen()
* and deleted on kdbClose().
