The `extern` keyword.

Property definitions

	# The `extern` keyword.
	var n_kwextern: TKwextern is writable, noinit

src/parser/parser_nodes.nit:1334,2--1335,46

	redef fun n_kwextern=(node)
	do
		_n_kwextern = node
		node.parent = self
	end

src/parser/parser_prod.nit:717,2--721,4