added event actions (by triggering gadgets) for global animations

This change adds a new option for the "graphicsinfo.conf" file for
defining clickable global animations that trigger other actions
(currently limited to triggering active gadget buttons on the same
screen as the global animations). The new option works like this:

global.anim_1.part_1.MAIN.anim_event:            click
global.anim_1.part_1.MAIN.anim_event_action:     tape.button.record

The second option is the new one (the first one already existed).
When clicking this global animation (on the main menu screen), the
game will be started (by triggering the "record" button on the tape
recorder, which effectively starts playing the current level).