The opening parenthesis in at annotations

Property definitions

	# The opening parenthesis in *at* annotations
	var n_opar: nullable TOpar = null is writable

src/parser/parser_nodes.nit:3064,2--3065,46

	redef fun n_opar=(node)
	do
		_n_opar = node
		if node != null then node.parent = self
	end

src/parser/parser_prod.nit:8671,2--8675,4