Adds an action to the @action_map.
If the action map already contains an action with the same name as @action then the old action is dropped from the action map.
The action map takes its own reference on @action.
a #GAction
2.32
See Implementation
Adds an action to the @action_map.
If the action map already contains an action with the same name as @action then the old action is dropped from the action map.
The action map takes its own reference on @action.