A list of vl-evatom-ps that describe the various
events. Verilog allows two kinds of syntax for these lists, e.g.,
one can write @(a or b) or @(a, b). The meaning is
identical in either case, so we just use a list of atoms.
Event controls are described in Section 9.7. We represent each
event controller as a vl-eventcontrol-p aggregates.