Make a new assert

Property definitions

nitc $ ASTBuilder :: make_assert
	# Make a new assert
	fun make_assert(n_id : nullable TId , n_expr : AExpr , n_else : nullable AExpr): AAssertExpr
	do
		return new AAssertExpr.make(n_id , n_expr , n_else)
	end
src/astbuilder.nit:114,2--118,4