Convert the event description list EVENT-DESC to an event type.
EVENT-DESC should contain one base event type (a character or symbol)
and zero or more modifier names (control, meta, hyper, super, shift, alt,
drag, down, double or triple). The base must be last.
The return value is an event type (a character or symbol) which
has the same base event type and all the specified modifiers. (fn EVENT-DESC)