formatting: simplify EBNF.
formatting: simplify EBNF.

tgunr/factor,factor/factor,factor/factor,bpollack/factor,bpollack/factor,bpollack/factor,mrjbq7/factor,bpollack/factor,mrjbq7/factor,bpollack/factor,tgunr/factor,tgunr/factor,mrjbq7/factor,tgunr/factor,tgunr/factor,bpollack/factor,bpollack/factor,tgunr/factor,mrjbq7/factor,mrjbq7/factor,factor/factor,factor/factor,factor/factor,factor/factor,mrjbq7/factor