This includes the following related or incidental changes:
* Remove the win_from_rects global variable. With one minor exception, they were all equal to the relevant render texture's size anyway.
* Split out time advancement from the handle_action function into a separate function
* Split out each individual button action into its own function
* Thanks to the above two, button actions triggered from the keyboard (and menu spells) no longer pass thru handle_action
* Side-effect: keyboard shortcuts and menu spells no longer trigger the button press animation
* Button presses now behave like proper buttons
* Button clicks are now grouped by effect in the handling code, rather than by index
* Removed a variable that mysteriously caused dialogue to become blank
